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PHY 112 > Chpt 20 > Flashcards

Chpt 20 Flashcards

1
Q
  1. What happens to the direction of a light ray when it enters a second medium? a) It always bends towards the normal b) It always bends away from the normal c) It bends except when entering along the normal d) It doesn’t bend it continues in a straight line
A

Answer: c) It bends except when entering along the normalExplanation: This is stated in the first paragraph of the text Refraction is the bending of light as it passes from one medium to another The direction of bending depends on the relative refractive indices of the two media If the light ray enters along the normal there is no bending

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2
Q
  1. When light travels from a rarer to a denser medium it bends: a) Towards the normal b) Away from the normal c) Along a parabolic path d) In a circular path
A

Answer: a) Towards the normal Explanation: This is illustrated in Figure 20.1 (a) and explained in the accompanying text When light enters a denser medium its speed decreases causing it to bend towards the normal

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3
Q
  1. What is the relationship between the angle of incidence and the angle of refraction according to Snell’s law? a) The ratio of their sines is constant b) They are always equal c) The sum of their tangents is constant d) The product of their cosines is constant
A

Answer: a) The ratio of their sines is constantExplanation: Snell’s law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given wavelength This constant is known as the refractive index of the second medium with respect to the first

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4
Q
  1. The absolute refractive index of a medium is defined as: a) The ratio of the speed of light in vacuum to the speed of light in the medium b) The ratio of the speed of light in the medium to the speed of light in vacuum c) The product of the speed of light in vacuum and the speed of light in the medium d) The sum of the speed of light in vacuum and the speed of light in the medium
A

Answer: a) The ratio of the speed of light in vacuum to the speed of light in the mediumExplanation: This is explicitly stated in the definition provided in the text The absolute refractive index gives a measure of how much the speed of light is reduced in a particular medium compared to its speed in a vacuum

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5
Q
  1. What does the term ‘optical invariant’ refer to in the context of refraction? a) The constant speed of light in a given medium b) The constant ratio of sines of angles in Snell’s law c) A specific relationship between refractive indices and angles of incidence and refraction d) The unchanging nature of the wavelength of light during refraction
A

Answer: c) A specific relationship between refractive indices and angles of incidence and refraction Explanation: The text explains the concept of optical invariant in section 20.2 It describes the relationship between the refractive indices of multiple media and the angles made by the light ray with the normal at each interface

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6
Q
  1. Under what condition does total internal reflection occur? a) When light travels from a denser medium to a rarer medium at any angle of incidence b) When light travels from a rarer medium to a denser medium at any angle of incidence c) When light travels from a denser to a rarer medium and the angle of incidence exceeds the critical angle d) When light travels from a rarer to a denser medium and the angle of incidence exceeds the critical angle
A

Answer: c) When light travels from a denser to a rarer medium and the angle of incidence exceeds the critical angle Explanation: Section 20.3 of the text defines total internal reflection and outlines the conditions for its occurrence It occurs when light traveling in a denser medium encounters the boundary with a rarer medium at an angle greater than the critical angle

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7
Q
  1. How is the critical angle for a glass-air interface calculated? a) By taking the inverse sine of the refractive index of glass b) By taking the inverse tangent of the refractive index of glass c) By taking the inverse cosine of the refractive index of glass d) By taking the square root of the refractive index of glass
A

Answer: a) By taking the inverse sine of the refractive index of glass Explanation: The computation of the critical angle is shown in section 20.3 The formula used involves taking the inverse sine of the ratio of the refractive index of the rarer medium (air) to the refractive index of the denser medium (glass)

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8
Q
  1. What is the main principle behind the functioning of optical fibers? a) Dispersion of light b) Diffraction of light c) Total internal reflection d) Refraction at plane surfaces
A

Answer: c) Total internal reflection Explanation: The text explains the application of total internal reflection in optical fibers in section 20.5 Light rays are guided through the fiber by repeatedly undergoing total internal reflection at the core-cladding boundary

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9
Q
  1. What kind of image does a converging lens form when the object is placed beyond its focal point? a) Virtual and erect b) Real and inverted c) Virtual and inverted d) Real and erect
A

Answer: b) Real and inverted Explanation: This information is related to the ray diagrams for converging lenses provided in Figure 20.9 When the object is located beyond the focal point the converging lens forms a real and inverted image on the opposite side of the lens

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10
Q
  1. What is the unit of power of a lens? a) Meter b) Diopter c) Watt d) Lumen
A

Answer: b) DiopterExplanation: This is stated in section 20.8 of the text The diopter is the unit of measurement for the optical power of a lens which is the reciprocal of its focal length in meters

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11
Q
  1. What is the main function of the human eye lens? a) To protect the eye from external damage b) To control the amount of light entering the eye c) To focus light onto the retina to form images d) To provide nourishment to the eye
A

Answer: c) To focus light onto the retina to form images Explanation: The role of the eye lens in vision is outlined in section 20.12 It acts as a converging lens that focuses incoming light rays onto the retina where photoreceptors convert light signals into electrical impulses for the brain to process

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12
Q
  1. What is Myopia? a) The inability to see distant objects clearly b) The inability to see near objects clearly c) Blurred vision due to astigmatism d) Loss of vision due to aging
A

Answer: a) The inability to see distant objects clearly Explanation: Myopia is explained as one of the optical defects of the eye in section 20.13 It’s a condition where the eyeball is too long or the lens is too powerful causing distant objects to be focused in front of the retina resulting in blurred vision

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13
Q
  1. Which type of lens is used to correct Myopia? a) Converging lens b) Diverging lens c) Cylindrical lens d) Bifocal lens
A

Answer: b) Diverging lens Explanation: The text states that Myopia can be corrected with spectacles using a suitable diverging lens The diverging lens spreads out the incoming light rays allowing them to focus correctly on the retina

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14
Q
  1. What is the main principle behind the functioning of a refracting telescope? a) Reflection of light b) Refraction of light c) Interference of light d) Diffraction of light
A

Answer: b) Refraction of light Explanation: The text describes the refracting telescope in section 20.14 It explains how the objective lens refracts light from distant objects to form an image which is then magnified by the eyepiece lens

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15
Q
  1. What is the function of a simple microscope (magnifying glass)? a) To view very distant objects b) To obtain a magnified image of small objects c) To project images onto a screen d) To correct astigmatism
A

Answer: b) To obtain a magnified image of small objects Explanation: Section 20.15 of the text discusses the simple microscope and its function It explains how a single convex lens can be used to magnify small objects by forming an enlarged virtual image

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16
Q
  1. How does a compound microscope differ from a simple microscope? a) It uses a single lens for magnification b) It uses two lenses for higher magnification c) It forms a real image d) It is used for viewing distant objects
A

Answer: b) It uses two lenses for higher magnification Explanation: The compound microscope is described in section 20.16 Unlike the simple microscope it utilizes two lenses - an objective lens and an eyepiece lens - to achieve greater magnification levels

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17
Q
  1. Where is the light-sensitive film located in a camera? a) In front of the lens b) Behind the lens c) At the focal point of the lens d) Inside the lens
A

Answer: b) Behind the lens Explanation: The text mentions the location of the light-sensitive film in a camera in section 20.17 It clarifies that the film is positioned behind the lens to capture the focused image formed by the lens

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18
Q
  1. What is the function of a periscope? a) To view objects that are directly in front of the observer b) To view objects that are otherwise inaccessible c) To magnify small objects d) To project images onto a screen
A

Answer: b) To view objects that are otherwise inaccessible Explanation: Section 20.18 of the text introduces the periscope and its purpose It explains how the periscope uses the principle of total internal reflection to allow observation of objects that are not in the direct line of sight

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19
Q
  1. What type of lenses do prism binoculars use? a) Convex lenses b) Concave lenses c) Cylindrical lenses d) Right-angled prisms
A

Answer: d) Right-angled prisms Explanation: The text describes prism binoculars in section 20.19 It highlights that prism binoculars utilize right-angled prisms to invert the image formed by the objective lens providing an upright view to the observer

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20
Q
  1. What is the main function of a projector? a) To view distant objects b) To magnify small objects c) To project slides or films onto a screen d) To correct vision defects
A

Answer: c) To project slides or films onto a screen Explanation: Section 20.20 of the text discusses the projector and its purpose It details how the projector utilizes a combination of lenses and light sources to enlarge and display images from slides or films onto a screen

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21
Q
  1. A light ray is incident on a water-air interface at an angle of 40° If the refractive index of water is 1.33 what is the angle of refraction in air? a) 28.9° b) 30.17° c) 58.75° d) 60°
A

Answer: a) 28.9° Explanation: This problem can be solved using Snell’s law n1sinθ1 = n2sinθ2 where n1 and n2 are the refractive indices of the first and second media respectively and θ1 and θ2 are the angles of incidence and refraction respectively In this case n1 = 1.33 (water) θ1 = 40° and n2 = 1 (air) Solving for θ2 gives sinθ2 = (n1/n2)sinθ1 = (1.33/1)sin40° = 0.855 Therefore θ2 = sin⁻¹(0.855) = 58.75°

22
Q
  1. The apparent depth of a swimming pool is less than its real depth due to: a) Reflection of light b) Refraction of light c) Diffraction of light d) Interference of light
A

Answer: b) Refraction of lightExplanation: When light from the bottom of the pool travels from water to air it bends away from the normal due to refraction This makes the pool appear shallower than it actually is

23
Q
  1. A fish is swimming in a pond To a person standing on the bank the fish appears to be: a) At its actual depth b) Deeper than its actual depth c) Shallower than its actual depth d) Displaced laterally but at the same depth
A

Answer: c) Shallower than its actual depth Explanation: This is a similar scenario to the previous question Due to refraction of light at the water-air interface the fish appears to be closer to the surface than it actually is

24
Q
  1. A ray of light traveling in glass enters air For what range of angles of incidence will the ray be totally internally reflected? a) For all angles of incidence b) For angles of incidence less than the critical angle c) For angles of incidence greater than the critical angle d) For no angle of incidence
A

Answer: c) For angles of incidence greater than the critical angle Explanation: Total internal reflection occurs only when the light ray is traveling from a denser to a rarer medium (glass to air in this case) and the angle of incidence exceeds the critical angle

25
Q
  1. What is the critical angle for a glass-air interface if the refractive index of glass is 1.5? a) 41.8° b) 48.2° c) 56.3° d) 60°
A

Answer: a) 41.8° Explanation: As shown in the text the critical angle can be calculated as sin⁻¹(n2/n1) where n2 is the refractive index of air (approximately 1) and n1 is the refractive index of glass (1.5 in this case) This gives a critical angle of 41.8°

26
Q
  1. A convex lens has a focal length of 10cm If an object is placed 20cm from the lens the image will be: a) Real inverted and magnified b) Real inverted and diminished c) Virtual erect and magnified d) Virtual erect and diminished
A

Answer: a) Real inverted and magnified Explanation: When an object is placed beyond the focal point of a converging lens the image formed is real inverted and magnified

27
Q
  1. A concave lens always forms an image that is: a) Real and inverted b) Real and erect c) Virtual and inverted d) Virtual and erect
A

Answer: d) Virtual and erect Explanation: A concave lens (diverging lens) always forms an image that is virtual erect and diminished regardless of the object’s position

28
Q
  1. Two thin lenses of focal lengths 20cm and 30cm are placed in contact What is the focal length of the combination? a) 10cm b) 12cm c) 25cm d) 50cm
A

Answer: b) 12cm Explanation: The formula for the focal length of a combination of thin lenses in contact is 1/f = 1/f1 + 1/f2 where f is the combined focal length and f1 and f2 are the focal lengths of the individual lenses Plugging in the given values and solving for f gives 12cm

29
Q
  1. A person with myopia can see clearly: a) Distant objects only b) Nearby objects only c) Both distant and nearby objects clearly d) Neither distant nor nearby objects clearly
A

Answer: b) Nearby objects onlyExplanation: Myopia is a condition where the eye focuses light in front of the retina making distant objects appear blurry People with myopia can see nearby objects clearly

30
Q
  1. Which of the following is NOT an optical instrument? a) Microscope b) Telescope c) Camera d) Thermometer
A

Answer: d) Thermometer Explanation: A thermometer is used to measure temperature not for manipulating light to form images unlike a microscope telescope or camera

31
Q
  1. What are the three main types of optical defects of the human eye?
A

Answer: The three main optical defects are myopia (nearsightedness) hyperopia (farsightedness) and astigmatismExplanation: Myopia causes difficulty in seeing distant objects hyperopia affects near vision and astigmatism leads to distorted vision due to irregular corneal shape

32
Q
  1. What is the purpose of using a converging lens in a refracting telescope?
A

Answer: A converging lens is used to gather and focus light from distant objects to form a clear image at the focal planeExplanation: It enhances the telescope’s ability to magnify objects by converging light rays effectively for observation

33
Q
  1. How does a magnifying glass work?
A

Answer: A magnifying glass uses a convex lens to bend light rays forming a virtual upright and magnified image of an objectExplanation: When the object is placed within the focal length of the lens the eye perceives a larger virtual image

34
Q
  1. Explain the term “tube length” in a compound microscope
A

Answer: Tube length refers to the distance between the objective lens and the eyepiece lens of a compound microscopeExplanation: It is typically standardized (e.g. 160mm) to ensure optimal magnification and image clarity

35
Q
  1. What is the relationship between the f-number of a camera lens and the brightness of the image formed?
A

Answer: The f-number (aperture) is inversely proportional to the image brightness; a smaller f-number allows more light resulting in a brighter imageExplanation: The f-number determines the amount of light entering the lens affecting exposure and depth of field

36
Q
  1. What is the function of the prisms used in binoculars?
A

Answer: Prisms in binoculars invert and redirect light rays to ensure the observed image is upright and aligned with the user’s viewExplanation: They use total internal reflection to minimize size while maintaining high-quality image orientation

37
Q
  1. Explain the role of the condensing lens in a projector
A

Answer: The condensing lens focuses and intensifies the light onto the slide or film ensuring uniform brightness across the projected imageExplanation: It improves light efficiency and ensures clarity in the enlarged display

38
Q
  1. Describe the difference between a convex and a concave lens in terms of their effect on parallel rays of light
A

Answer: A convex lens converges parallel rays to a focal point while a concave lens diverges them making the rays appear to originate from a focal pointExplanation: Convex lenses focus light for applications like magnification whereas concave lenses spread light to correct vision defects

39
Q
  1. What is spherical aberration and how can it be minimized in lenses?
A

Answer: Spherical aberration occurs when light rays passing through the edges of a lens focus at different points than rays passing through the center causing a blurred imageExplanation: It can be minimized by using aspherical lenses applying lens coatings or combining lenses of different shapes

40
Q
  1. Describe the concept of “conjugate points” in the context of lenses
A

Answer: Conjugate points are pairs of points where an object placed at one point forms an image at the other and vice versa with a specific lensExplanation: This relationship allows precise image formation in optical systems like microscopes and projectors

41
Q
  1. Snell’s law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for two given media Mathematically n₁sinθ₁ = n₂sinθ₂ This law defines how light bends when passing from one medium to another governed by the refractive indices (n₁ and n₂) of the two media
A
42
Q
  1. The refractive index of a medium is the ratio of the speed of light in a vacuum to its speed in that medium It quantifies how much light slows down and bends when entering the medium Higher refractive indices indicate greater bending
A
43
Q
  1. Total internal reflection occurs when a light ray traveling from a denser to a rarer medium hits the interface at an angle greater than the critical angle and reflects back into the denser medium This phenomenon is the basis for optical devices like prisms and fibers as no light escapes the medium
A
44
Q
  1. Optical fibers transmit light through multiple total internal reflections within a thin flexible core surrounded by cladding Light remains trapped within the core due to the refractive index difference between the core and cladding ensuring minimal signal loss
A
45
Q
  1. The two types are convex (converging) and concave (diverging) lenses Convex lenses bulge outward and focus light to a point while concave lenses curve inward and spread light out Convex lenses are used to magnify or focus images while concave lenses correct issues like myopia by diverging light
A
46
Q
  1. Focal length is the distance from the lens to the focal point where parallel rays converge or appear to diverge It determines the lens’s converging or diverging power measured in centimeters or meters
A
47
Q
  1. A real image is formed when light rays converge at a point and can be projected on a screen while a virtual image is formed when rays diverge and cannot be projected Examples include camera images (real) and mirror reflections (virtual)
A
48
Q
  1. It is the eye’s ability to change the focal length of the lens to focus on objects at varying distances The ciliary muscles adjust the lens’s curvature enabling sharp vision for both near and far objects
A
49
Q
  1. Astigmatism occurs when the cornea or lens has an irregular shape causing blurred or distorted vision This results in light focusing unevenly on the retina which is corrected using cylindrical lenses
A
50
Q
  1. A simple microscope uses a single lens for magnification while a compound microscope uses two lenses (objective and eyepiece) for higher magnification The compound design allows greater detail and is widely used in scientific studies
A

PHY 112 (6 decks)

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