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Physics Paper 2 > P14 Light > Flashcards

P14 Light Flashcards

1
Q

What’s the range of wavelengths of visible light?

A

400nm - 700nm

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2
Q

When a wave refracts, what property is conserved out of wavelength, frequency and wave speed?

A

Frequency - directly proportional to energy (conservation of energy)

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3
Q

Besides refraction, what can happen to a wave at a boundary?

A

Reflection, transmission, absorption

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4
Q

describe the relationship between colour and frequency

A
  • Every colour of visible light corresponds to a specific frequency
  • Continuous spectrum
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5
Q

what is the function of lasers?

A

Produce light that is monochromatic and coherent

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6
Q

how do colour filters work?

A
  • work by absorbing certain wavelengths
  • and transmitting other wavelengths
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7
Q

Why do certain objects have certain colours?

A
  • Certain wavelengths of visible light are reflected or transmitted and other wavelengths are absorbed
  • The colours we see are the wavelengths that are reflected or transmitted
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8
Q

Why are red, blue and green the primary colours of light?

A

Because they can be mixed to produce other colours

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9
Q

What makes an object appear white or black?

A

Black - all wavelengths absorbed
White - all wavelengths reflected or transmitted equally

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10
Q

What is meant by opaque?

A
  • Opaque objects don’t transmit any light
  • They absorb scatter and/or reflect all wavelengths of visible light
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11
Q

What are pigments?

A
  • Chemicals that absorb and reflect different wavelengths of visible light
  • A red pigment will reflect wavelengths corresponding to red and absorb all other wavelengths
  • Objects that appear white have no pigment; all wavelengths are reflect equally
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12
Q

What is meant by transparent and translucent?

A
  • Transparent objects transmit all wavelengths of visible light, without any refraction
  • Translucent objects scatter or refract light that passes through them, due to internal boundaries within the material that repeatedly change the direction of the light
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13
Q

What do waves transfer?

A

Energy

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14
Q

What causes a transverse wave?

A

Oscillations that are perpendicular to the direction of energy transfer

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15
Q

Describe how optical density affects the speed of the light wave travelling through it

A

The higher the optical density, the lower the speed of light through it

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16
Q

Imagine a light ray entering a less optically dense medium at 40 to the normal. How does the angle of refraction compare to the angle of incidence?

A

The angle of refraction is greater than the angle of incidence

17
Q

How are wavelength and frequency affected when a wave is refracted?

A
  • Frequency does not change
  • Wavelength changes (either increases or decreases)
18
Q

What happens when a light ray travels from a more optically dense material to a less optically dense material?

A

Light rays passing from a more dense to a less dense medium bend away from the normal. The angle of refraction is greater than the angle of incidence.

19
Q

What happens when a light ray travels from a less optically dense material to a more optically dense material?

A

Light rays passing from a less dense to a more dense medium bend towards the normal. The angle of incidence is greater than the angle of refraction

20
Q

Light path through convex (converging) lenses

A

When light rays enter a lens they are refracted as they enter and then again as they leave the lens

21
Q

Drawing ray diagrams to show images formed by convex lenses

A
  • Draw one ray from the top of the object, parallel to the principal axis which refracts through the principal focus
  • Draw a ray from the top of the object directly through the centre of the lens (no refraction)
  • Where the two rays meet is the top of the image
22
Q

Description of the image formed by convex lenses

A
  • Inverted
  • Either smaller of magnified
  • Real
  • Close to the object, the image is virtual, magnified and upright
  • Further than focal length from the object, the image is inverted, real and larger
  • Beyond twice the focal length, the image is inverted, real and smaller
23
Q

Concave (diverging) lens

A
  • Concave lenses make parallel rays spread out (diverge)
  • The rays seem to come from a ‘virtual focus’ on the other side
  • Concave lenses are diverging lenses
  • Used to correct short sight
24
Q

Drawing ray diagrams to show images formed with concave lenses

A
  • Draw a ray from the top of the object diagonally through the centre of the lens
  • Draw one ray from the top of the object to the lens, parallel to the principal axis
  • Draw a dotted line from the principal focus in front of the lens to the point where the ray parallel to the principal axis crosses the lens
  • Extend that same ray beyond the lens with a solid arrow to show the ray diverging from the lens
  • Where the two rays meet is the top of the image
25
Q

Description of an image formed by concave lenses

A
  • Always the right way up
  • Always smaller
  • Always produce a virtual image
26
Q

How to calculate the magnification produced by a lens

A

magnification = image height / object height

27
Q

What is the principal focus of a convex lens?

A

The place where all the rays hitting the lens parallel to the axis meet

28
Q

What is meant by focal length?

A

The distance from the lens to the principal focus

29
Q

What is a virtual image?

A
  • A virtual image is an image formed by the eye/brain of the observer when the brain assumes that diverging rays entering the eye must have travelled in straight lines from a source.
  • A virtual image is not real, so it cannot be picked up on a screen - the rays do not cross at the point in is formed at. Instead rays have to be traced back in a straight line to that point.
30
Q

Explain the difference between a real and virtual image

A
  • A real image of a point on an object is formed where rays of light converge at a point
  • If a screen is placed at that point the image will appear on the screen
31
Q

what are transparent objects?

A
  • transmit all the incident light that enters the object
  • no light is absorbed at the surface
  • the transmitted light travels through the object
32
Q

what are translucent objects?

A
  • let light pass through them, but the light is scattered or refracted
  • because there a lot of internal boundaries that change the direction of the light rays repeatedly
33
Q

what is an opaque object?

A
  • an object that absorbs all the light that reaches it
  • the light is either reflected, scattered at the surface, or absorbed by the object
  • no light travels all the way through the object
34
Q

what is the difference between the image produced by a concave and convex lens?

A

the image produced by a convex lens can be either virtual or real, but the image produced by a concave lens is always virtual

35
Q

what is a perfect black body?

A
  • an object that absorbs all of the radiation incident on it
  • a black body does not reflect or transmit any radiation

Physics Paper 2 (11 decks)

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