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AQA GCSE Physics (Detailed Version) > P14 - Light > Flashcards

P14 - Light Flashcards

1
Q

What is the angle of incidence?

A

The angle between the incident ray and the normal

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2
Q

What is the angle of reflection?

A

Angle between the reflected ray and the normal

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3
Q

What is a concave lens?

A

A lens that makes parallel rays diverge (spread out)

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4
Q

What is a convex lens?

A

A lens that makes light rays parallel to the principal axis converge (meet) at a point

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5
Q

What is diffuse reflection?

A

Reflection from a rough surface - the light rays are scattered in different directions

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6
Q

What is the focal length?

A

The distance from the centre of the lens to the point where light rays parallel to the principal axis are focused

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7
Q

What is magnification?

A

image height / object height

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8
Q

What is a magnifying glass?

A

A converging lens used to magnify a small object which must be placed between the lens and its focal point

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9
Q

What is the normal line?

A

A straight line through a surface or boundary perpendicular (90°) to the surface or boundary

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10
Q

What is an opaque object?

A

An object which light cannot pass through, instead the object absorbs or reflects the light

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11
Q

What is the principal focus?

A
  • The point where light rays parallel to the principal axis of a lens are focused for a convex lens
  • Where the light rays appear to originate from a concave lens
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12
Q

What is a real image?

A

An image formed by a lens that can be projected onto a screen

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13
Q

What is refraction?

A

The change of direction of a light ray as it passes across a boundary between 2 transparent substances

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14
Q

What is specular reflection?

A

Reflection from a smooth surface. Each light ray is reflected in a single direction

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15
Q

What is a translucent object?

A

An object that allows light to pass through, but the light is scattered or refracted as it does so, due to lots of internal boundaries in the object

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16
Q

What is a transparent object?

A

An object that transmits all the incident light that enters the object

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17
Q

What is a virtual image?

A

An image, seen in a lens or a mirror, from which light rays appear to come after being refracted by a lens or reflected by a mirror. They cannot be projected onto a screen

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18
Q

When would sound be relfected?

A

In an echo

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19
Q

What is the law of reflection?

A

The angle of incidence = the angle of reflection

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20
Q

What is reflection on a smooth surface known as and why?

A
  • Specular reflection: parallel light rays reflected in a single direction
  • Light rays are not scattered
  • Incident angles are the same
  • Angles of reflection are the same
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21
Q

What is reflection on a rough surface known as and why?

A
  • Diffuse reflection occurs when parallel light rays hit a rough surface.
  • The rough surface scatters the light rays in different directions.
  • Incident angles vary due to the roughness.
  • As a result, angles of reflection also differ.
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22
Q

What happens to the velocity of a wave as it travels from an optically rare medium to an optically dense medium?

A

decreases

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23
Q

What happens to the wavelength of a wave as it travels from an optically rare medium to an optically dense medium?

A

Decreases

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24
Q

What happens to the frequency of a wave as it travels from an optically rare medium to an optically dense medium?

A

does not change

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25
Q

What happens to the direction of a wave as it travels from an optically rare medium to an optically dense medium?

A

bends towards the normal

26
Q

What happens to the velocity of a wave as it travels from an optically dense medium to an optically rare medium?

A

Increase

27
Q

What happens to the frequency of a wave as it travels from an optically dense medium to an optically rare medium?

A

Does not change

28
Q

What happens to the direction of a wave as it travels from an optically dense medium to an optically rare medium?

A

bends away from the normal

29
Q

What causes refraction?

A

Waves change speed as they pass between substances of different densities, this causes them to change direction

30
Q

What is the law of refraction?

A
  • Light ray entering denser medium: bends towards normal, angle of refraction < angle of incidence.
  • Light ray entering less dense medium: bends away from normal, angle of refraction > angle of incidence.
31
Q

Describe what occurs when light travels from air into a glass block and then back out into air:

A
  • Light slows down entering glass (glass > air density).
  • Wavelength decreases in glass.
  • Direction shifts towards the normal in glass.
  • Light speeds up exiting glass (air < glass density).
  • Wavelength increases in air.
  • Direction shifts away from the normal in air.
32
Q

READ ONLY:

Describe the investigation in order to investigate refraction of light:

A

1) Place the glass block in the centre of the piece of paper and draw around the perimeter of the box
2) remove the block and draw a dotted normal line perpendicular to the edge of the long side of the block, roughly half way along
3) Draw a line to represent the incident ray 30* to the normal
4) Place the glass block back within the rectangle you have drawn
5) Switch on the ray box with a narrow slit in front of the light bulb and shine the ray along the incident ray you have drawn
6) Observe the path of the light through the block and out the other side
7) Mark the path of the emergent light ray on the other side
8) Remove the glass block. Draw a normal at the point where the light emerged from the glass block.
9) Draw a line to join the incident ray and emergent ray through the rectangle representing the glass block to give the refracted ray
10) Measure the incident and refracted angles
11) Repeat experiment with a range of angles for the incident ray
12) Repeat experiment and find mean average for each result

*Possible inaccuracies:
The width of the light ray may make it difficult to draw along the centre of the line

33
Q

Explain what happens if white light is shone through a prism

A
  • White light = all colors of spectrum
  • Colors = different frequencies, wavelengths
  • Glass of prism = different speeds for colors
  • Refraction = colors split in prism
34
Q

What is the wavelength and frequency of Violet light (closest to ultraviolet and x rays)

A

short wavelength, high frequency

35
Q

What is the wavelength and frequency of red light (closest to infrared and microwaves)

A

long wavelength, low frequency

36
Q

Why are some lights different colours?

A

Light is a type of electromagnetic wave. The only difference between the different colours of light are the wavelength / frequency of the electromagnetic wave

37
Q

What is said to happen when white light splits up into separate colours?

A

White light has been dispersed

38
Q

What light is refracted the most?

A

Violet (short wavelength, high frequency)

39
Q

What light is refracted the least?

A

Red light (long wavelength, low frequency)

40
Q

How do colour filters work?

A

They absorb certain wavelengths and transmit other wavelengths

41
Q

What will happen as white light travels towards a blue filter?

A

A blue filter will transmit blue light and absorb all other wavelengths of light

42
Q

What will happen if red light travels towards a green filter?

A

The red light would be absorbed, allowing no light to be transmitted

43
Q

What determines a materials colour?

A
  • Pigments are chemicals that absorb specific wavelengths of light.
  • They reflect the wavelengths they do not absorb.
  • Example: A red pigment reflects red light and absorbs other wavelengths.
  • This gives surfaces their color appearance.
44
Q

What pigments does a white surface contain?

A

A white surface has no pigments, therefore it reflects any light

45
Q

Why would an object appear black?

A

If it absorbs all wavelengths of light

46
Q

What colour would a blue object appear through a red filter?

A
  • Blue object + red filter = appears black.
  • Blue objects reflect blue light.
  • Red filter transmits only red light.
  • Blue light absorbed by filter.
  • No reflected light = object looks black.
47
Q

What colour would a white object appear through a green filter?

A
  • White object reflects all wavelengths of light.
  • Green filter transmits only green light.
  • Object viewed through green filter reflects green light.
  • Therefore, object appears green when viewed through green filter.
48
Q

What are the units for magnification?

A

Magnification does not have units as it is a ratio

49
Q

Is the image formed by a magnifying glass real or virtual (when the magnifying glass is used correctly)?

A

Virtual, this is because only the person using the magnifying glass can see the image. The image cannot be projected onto a screen

50
Q

How does a magnifying glass work?

A

A magnifying glass is a convex lens used to make an object appear much larger than it actually is. This works when the object is placed at a distance less than the focal length from the lens.

51
Q

READ ONLY:

How do you draw a ray diagram for a convex lens?

A

1) Draw a ray passing from the object through the optical centre of the lens
2) Draw a ray which is parallel to the principal axis, which refracts through the lens and passes through the principal focus
3) Draw a ray which passes through the principal focus (on the same side as the object) and is then refracted through the lens, emerging parallel to the principal axis
4) The point at which the lines cross is where the image is formed

52
Q

READ ONLY:

How do you draw a ray diagram for a concave lens?

A

1) Draw a ray that passes from the object through the optical centre of the lens
2) Draw a ray which is parallel to the principal axis, which refracts through the lens and refracts away from the principal axis (It should refract so that if the ray was continued backwards, it would pass through the principal focus)
3) The point where the rays cross is where the image is formed

53
Q

Describe the nature of the image formed from a convex lens when the object is at infinity

A

The image is formed at f, the image is real, the image is inverted, the image is diminished

54
Q

Describe the nature of the image formed from a convex lens when the object is beyond 2f

A

The image is formed between f and 2f, the image is real, the image is inverted, the image is diminished

55
Q

Describe the nature of the image formed from a convex lens when the object is at 2f

A

The image is formed at 2f, the image is real, the image is inverted, the image is the same size

56
Q

Describe the nature of the image formed from a convex lens when the object is between f and 2f

A

The image is formed beyond 2f, the image is real, the image is inverted, the image is magnified

57
Q

Describe the nature of the image formed from a convex lens when the object is at f

A

As the rays are parallel, they never converge, therefore no image is formed

58
Q

Describe the nature of the image formed from a convex lens when the object is closer to the lens that f

A

The image is virtual, the image is upright, the image is magnified

59
Q

Describe the nature of the image formed from a concave lens

A

The image is formed closer the lens than f (and the object), the image is virtual, the image is upright, the image is diminished

60
Q

Describe the image formed by a plane mirror

A

The image is virtual, upright, the same size as the object, and the same distance behind the mirror as the object is infront

61
Q

What 3 things may occur when a wave arrives at a boundary?

A

• The wave may be absorbed by the material the wave is trying to cross into - this transfers energy to the materials energy stores
• The wave may be transmitted - the waves carry on travelling through the new material. This often leads to refraction
• The wave is reflected

62
Q

How does a camera work?

A

A convex lens is used to produce a real image of an object on a film (or an array of pixels for a digital camera). The position of the lens is adjusted to focus the image on the film

AQA GCSE Physics (Detailed Version) (27 decks)

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