SP5 - Light and the Electromagnetic Spectrum ✓ Flashcards

1
Q

SP5a - Describe total internal reflection.

A
  • When light passes from water or glass into air, the ray could be totally internally reflected.
  • When the angle of incidence is greater than the critical angle, then the light is completed reflected inside the block.
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2
Q

SP5a - What can i and r represent in ray diagrams?

A
  • i: Angle of incidence (between incident ray and the normal)
  • r: Angle of reflection/refraction (between reflected/refracted ray and the normal)
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3
Q

SP5a - What is the normal?

A

The line drawn perpendicular to the object light is reflecting off (or refracting through)

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4
Q

SP5a - What is the relation between the angles of incidence and reflection?

A

i = r (Angle of incidence = angle of reflection)

This is the law of reflection

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5
Q

SP5a - What two processes can be shown using a ray diagram?

A
  • Reflection
  • Refraction
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6
Q

SP5a CP - Describe a method to explore refraction with varying angles of incidence,

A
  • Place a ray box with a slit in front of it on a piece of paper
  • Place a glass box the way of the ray of light thta is being produced
  • Draw around the glass block
  • Mark the point of entry and exit for the light aswell as two further points (such as origin and edge of paper) on the piece of paper
  • Use your markings to draw lines representing the travel of the ray of light
  • Repeat with ray box at different angles and compare your results
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7
Q

SP5b - Describe why a green object appears green in sunlight.

A
  • Sunlight is made up of white light as it contains all the colours of the visible spectrum
  • An object that appears green will reflect the green part of the spectrum but abosrb all the other colours
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8
Q

SP5b - What are the two types of reflection?

A
  • Specular: When light is reflected evenly on a smooth surface
  • Diffuse: When light is reflected in all directions on a rough surface
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9
Q

SP5b - Why do some objects appear black / white?

A
  • White objects reflect all colours
  • Black objects absorb all colours
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10
Q

SP5c - When an object is placed more than 2F from a converging lens, what kind of image is created?

A
  • Diminished
  • Inverted
  • Real Image
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11
Q

SP5c - What does F mean on a ray diagram?

A

F is the focal length, i.e the length between the lens and its focal point

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12
Q

SP5c - What happens when an object is placed between 2F and F from a converging lens?

A

The image is:

  • Magnified
  • Real
  • Inverted
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13
Q

SP5c - What happens when an object is placed less than F from a converging lens?

A
  • Magnified
  • Virtual
  • Right way up
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14
Q

SP5c - What type of image do diverging lens always form?

A

Images that are:

  • virtual
  • same way up
  • much closer to the lens
  • much smaller
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15
Q

SP5c - What is a lens, and what is its power?

A

A lens is a small piece of transparent material made to refract light in a certain way

The power of a lens is how much it refracts light and is dependant on the shape and thickness of the lens

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16
Q

SP5c - When an object is placed at 2F from a converging lens, what happens?

A
  • Real image
  • Inverted
  • 2F from other side of lens
  • Same size
  • (Photocopier)
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17
Q

SP5c - What is the difference between real and virtual images?

A
  • A real image can be projected onto a screen whereas virtual image cannot be projected onto a screen.
  • Real images are formed by light rays that come together.
  • Virtual images seem to be on the same side of the lens as the object
18
Q

SP5c - What is the focal point of a lens?

A

The point where all the rays of light would converge onto and meet.

19
Q

SP5c - What is the difference between a converging (convex) and diverging (concave) lens?

A
  • Converging: Fatter in the middle and thinner at the top and bottom. Rays of light converge onto a focal point
  • Diverging: Fatter at the top and bottom and thinner in the middle. Rays diverge away from each other once they pass through
20
Q

SP5d - How were infrared waves discovered?

A
  • A prism was used to refract white light into the seven componets.
  • A thermometer was placed just outside of the red part of this spectrum.
  • Another was placed in the spectrum.
  • The thermometer next to red was warmer suggesting there was something warming it up
21
Q

SP5d - What are the similarities between all EM waves?

A
  • They are all transverse waves
  • They all travel at (3x10^8m/s) ina vacuum
  • They transfer energy
22
Q

SP5e - List all of the EM waves in order of increasing wavelength/decreasing frequency.

A
  • Gamma rays
  • X-rays
  • Ultraviolet
  • Visible light
  • Infrared
  • Microwaves
  • Radio waves
23
Q

SP5e - List all the colours in the visible light spectrum.

A

ROYGBIV

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet
24
Q

SP5e - Why do different telescopes need to be used to study different EM waves?

A

EM waves of different length get absorbed by different amounts by the atmosphere

25
Q

SP5f - How are radio waves produced?

A
  • Oscillations in electrical circuits.
  • Metal rods can be used as aerials because they can absorb and transmit these oscillations
26
Q

SP5f - What can infrared be used for?

A
  • Heating food
  • Short range communication such as TV remotes
  • Security systems
27
Q

SP5f - What can microwaves be used for?

A
  • Communications and satellite transmissions
  • Heating up food and giving it energy
28
Q

SP5f - What can radio waves be used for?

A
  • Transmitting radio broadcasts
  • Radio communications via satellites
29
Q

SP5f - Whay can radio waves be used for longer ranges than microwaves?

A
  • The way radio waves and microwaves travel is dependant on the angles they reach the ionosphere.
  • At all angles, microwaves pass straight through and so there is maximum range they can be fired in a straight line.
  • At some angles, radio waves are reflected by the ionosphere, because they have larger wavelengths.
  • This means they don’t have to be fired directly to a point
30
Q

SP5g - Describe the greenhouse effect in terms of radiation.

A
  • Energy from the sun is absorbed by the earth.
  • The earth radiates this into the atmosphere
  • Greenhouse gases in the atmosphere absorb this energy keeping it in the atmosphere
  • This means that the earth doesn’t radiate into the atmosphere the same amount of energy it absorbed
  • Thus the temperature of the earth rises
31
Q

SP5g - For the earth’s temperature to stay constant what must happen?

A

The amount of radiation it absorbs from the sun must be equal to the amount of radiation that the earth radiates into space

32
Q

SP5g - What is the difference between a hot and cold object in terms of radiation?

A
  • All objects emit the same amount of radiation that they absorb.
  • Hotter objects will emit more radiation than cold objects in the same time
33
Q

SP5g CP - Describe an experiment to explore how different surfaces absorb and emit infrared radiation using the following surfaces:

  • Shiny black
  • Shiny silver
  • Dull black
  • Dull grey
A
  • Pour water at 80° into four boiling tubes
  • Cover each with one of the surfaces
  • Put a thermometer in each
  • Time it and record the temperautre at regular intervals
  • The one that has the largest drop in temperature emits the most energy and thus must also absorb the most energy
  • You would expect the results to be from largest to smallest change:
  1. Dull grey
  2. Dull black
  3. Shiny black
  4. Shiny silver
34
Q

SP5h - What are the uses of gamma radiation?

A
  • Radiotherapy
  • Sterilisation of medical equipment and food
  • PET scanner
35
Q

SP5h - What are the uses of Ultraviolet rays?

A
  • Disinfect waters by killing microorganisms
  • Invisible ink due to fluoresence
  • Security on bank notes
36
Q

SP5h - What are the uses of x-rays?

A

Imaging of the inside of the body

37
Q

SP5i - What are the dangers of infrared radiation?

A
  • Infrared radiation is absorbed by our body.
  • We feel it as heat and an excess of it can destroy cells burning skin
38
Q

SP5i - What are the dangers of ultraviolet light?

A

It can cause sunburn and damage to DNA which can lead to skin cancer

39
Q

SP5i - What are the dangers of x-rays and gamma rays?

A

They can lead to mutations causing cancer.

40
Q

SP5i - Why are UV x-rays and gamma rays dangerous?

A
  • They are ionising radiation.
  • They large amounts of energy due to high frequencies and short wavelengths which can pass through our skin.