Ch 9. Ray Optics And Optical Instruments Flashcards
The radius of curvature of each surface of a biconvex lens is 20cm and the refractive index of the material of the lens is 1.5.
The focal length of the lens is
20 cm
A convex lens of focal length 40 cm and a concave lens of focal length 29 cm are in contact. The power of their combination in diootre is
-2.5
Light year is equal to
9.46 × 10¹⁵
A spherical mirror is immersed in water. It’s focal length will
Remain same
The coefficient of reflection for total internal reflection will be
1
The critical angle for total internal reflection of a ray from any medium to vaccum is 30•Degree. Then velocity of light in the medium will be
μ = 1/sinC, Va/Vm = 1/sinC, Vm = 3× 10⁸ × 1/2 = 1.5 × 10⁸ m/s
V niche a, V niche m, V niche m
In visible spectrum, which colour has larger wavelength
Red
The dispersive power of a prism depends on
Nature of material of prism
The final image formed by a terrestrial telescope is
Virtual and erect compared to the object
The unit of which physical quantity is light year?
Distance
Which of the following is correct for refractive index of mean colour (yellow colour) ?
µ = µr + µv/2
Neeche r and v
Power of parallel sided glass-slab is
Zero
Angular dispersion is equal to
(µv - µr) A
Neeche v and r
Which of the following relations is correct for dispersive power?
ω = µv - µr/µy - 1
Neeche v, r and y
Velocity of light in vacuum is c. its value in glass
(µ = 3/2) will be
2c/3
The power of convex lens of focal length 20 cm in dioptre is
5
The velocity of light is maximum in
Vaccum
The refractive index of diamond is about
2.42
Optical path is equal to
Refractive index × path-length
A convex lens (µ = 1.5) is immersed in water
(µ = 1.33), then it will behave as
Converging lens
Light owes its colour to its
Frequency
The solar spectrum is
Continuous
Which one of the following has maximum refractive index?
Diamond has maximum refractive index
Equivalent focal length of two lenses in contact having power
-15D and +5D will be
-10cm
A convex lens is dipped in a liquid, whose refractive index is equal to refractive index of material of lens. Then it’s focal length will
Become infinite
Critical angle for light moving from medium I to medium II is θ. The speed of light in medium I is v. Then speed in medium II is
V/Sin θ
Magnifying glass is to be used at the fixed object distance of 1 inch. if it is to produce an erect mage 5 times magnified, its focal length should be
1.25”
Which of the following phenomena takes place when monochromatic light is incident on a prism?
Dispersion
The critical angle of light passing from glass to air is minimum for
Violet colour
The angle of minimum deviation for thin prism of refractive index (µ) is
(µ -1) A
The focal length of a lens
µ = 1.5 in air is 20cm. Its focal length in medium of refractive index 1.5 is
♾️
The optical fibre works on the principle of
Total internal reflection
Transverse nature of light is shown by
Polarization
When to converging lenses of same focal length f are placed in contact, then the focal length of the combination is
f/2
How many images are formed by the lens if an object is kept on its axis?
µ₁ µ₃
µ₂ µ₄
2
Statement 1st : For focal length of a convex lens
1/f = (µ-1) (1/r₁ - 1/r₂)
Statement 2nd : for local length of red colour of light is maximum
Both the statements are true, but Statement 2 is not the correct explanation of statement 1
For the following question number 28 to 30 A paragraph is a given. You have to first go through that given paragraph and then answer the following three questions by indicating correct option.
Paragraph
When a ray passes through a prism, refraction takes place as shown in figure :
Q. Angle of emergence is
<r₂
<Angle sign
Angle α is
(180° - A)
When a ray passes symmetrically through a prism it suffers minimum deviation. Here <r is
<Angle sign
A/2
When a ray of light enters a glass slab, its wavelength
Decreases
Image formed by a concave spherical mirror is
Virtual, Real, Magnified, Inverted
Ans - All of the above
A biconvex lens (µ = 1.5) has equal curvature each of 20 cm.
The power of the lens is
5 D
Monochromatic light of wavelength 6000 A in vacuum enters a medium of refractive index 1.5. The wavelength of it in this medium is
4000A°
When light travels from one medium to another which of the following factors change?
Wavelength and frequency
Both A and B
If angle of incidence is
i’ > i, then angle of refraction is
< i’
If angle of incidence is
i’ > 2 i, then angle of refraction is
< 2i
For what value of angle of incidence total internal reflection (TIR) takes place?
For No value
The image formed at the retina of human eye is
Inverted
A path length t in a glass of refractive index n is equivalent to —– path length in vacuum.
nt
The radius of curvature of plane mirror is
Infinite
SI unit of power of lens is
Dioptre
Statement 1: Light travels in a straight line in a homogeneous medium
Statement 2 : in diffraction light changes its path without any change in the medium
Statement 1 is true, but Statement 2 is false.
₁µ₂ is equal to
µ₂/µ¹
Which of the following is the cause of formation of rainbow?
Refraction
The focal length of a lens of capacity 4 dioptre is
0.25 m
If the focal length of a glass lens (µ = 3/2) in air is f a and in water (µ = 4/3) is f w then
a and w neeche
fw = 4fa
w and a neeche
Which of the following relations is correct for intensity of scattered light ( I ) and wavelength of light (λ)?
I ∝ 1/λ⁴
Power of two lenses in contact is
P = P₁ + P₂
If µ g = 3/2 and µ w = 4/3 then w µ g is
Neeche g and w and w and g again
9/8
Critical angle for glass is
42° (nearly)
Critical angle for transparent medium diamond is
24.41°
The refractive index of material of the prism is
µ = sin (A+δm/2)/sin A / 2
Neeche m
Which of the following is correct for astronomical telescope?
fo > fe
Neeche o and e
The image formed by simple microscope is
Virtual and erect
Which of the following eye defects is removed by convex lens?
Far sightedness
Focal length of eye lens of a healthy man is about
25cm
The length of an astronomical telescope for normal adjustment is
fo + fe
Neeche o and e
On increasing the length of the tube of compound microscope, magnifying power
Increases
The lens which is used to remove short sightedness is
Concave
Which of the relations is correct for the magnifying power of compound microscope?
M = - L/f₀ ( 1 + D/fe)
Neeche e
The magnifying power of an astronomical telescope for normal adjustment is
- f₀/fe
Neeche e
Cylindrical lenses are used to correct the eye defect called
Astigmatism
The image formed by objective lens of a compound microscope is
Real and Large
Which lens is used to remove hypermetropia?
Convex
The resolving power of human eye (in minute) is
1/60
What lens does a short sighted person uses for clear vision?
Concave lens
When the tube length of microscope is increased, its magnifying power
Increases
The final image in astronomical telescope is
Virtual and inverted
The magnifying power of magnifying glass of power 12 dioptre is
4
Image formed on retina is
Real and inverted
Magnifying power of simple microscope is
M = 1 + D/f
