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GCSE Physics Unit 2 > Light > Flashcards

Light Flashcards

1
Q

What are objects that produce light called?

A

Luminous

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2
Q

What are non-luminous objects?

A

Objects that we see because light from luminous sources reflects off them and into our eyes.

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3
Q

What are transparent materials?

A

Materials through which light easily travels

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4
Q

What are opaque materials?

A

Materials through which light cannot travel.

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5
Q

What is the light ray striking a mirror called?

A

The incident ray

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6
Q

What is the light ray travelling away from the mirror called?

A

The reflected ray.

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7
Q

With what are the angles of incidence and reflection measured?

A

The normal

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8
Q

What is the Law of Reflection?

A

The angle of incidence is always equal to the angle of reflection.

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9
Q

Experiment to prove the law of reflection [10]

A
  1. Draw a straight line AOB on a sheet of white paper.
  2. Using a protractor, draw a normal at O.
  3. Using the protractor, draw straight lines at angles between 15 and 75 degrees to the normal.
  4. Rest a plane mirror on the line AOB.
  5. Using a ray box, shine a ray of light along the 15 degree line.
  6. Mark two crosses on the paper along the reflected ray.
  7. Remove the mirror and use a ruler to draw a line joining the crosses and to point O. This is the reflected ray.
  8. Using a protractor, measure the angle of reflection.
  9. Record in a table the angles of incidence and reflection.
  10. Repeat for various angles between 15 and 75 degrees.
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10
Q

What is the image in a plane mirror?

A

Virtual, the same size as the object, laterally inverted and the same distance behind the mirror as the object is in front.

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11
Q

What is refraction?

A

The change of direction of a beam of light as it travels from one material into another.

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12
Q

Why does refraction occur?

A

Because light travels at different speeds in different materials.

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13
Q

Is the speed of light in water lower or higher than the speed of light in air?

A

Lower

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14
Q

When refraction occurs, what always happens to some of the light?

A

Some of the light is always reflected internally.

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15
Q

When light slows down, what happens?

A

It bends towards the normal.

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16
Q

When light speeds up, what happens?

A

It bends away from the normal.

17
Q

Through what material does light travel the fastest?

A

Air.

18
Q

What is dispersion?

A

The breaking up of white light into its component colours.

19
Q

Why does dispersion occur in glass?

A

Each colour of white light travels at the same speed in air but at slightly different speeds in glass.
This means that each colour bends at a slightly different angle when it refracts.

20
Q

Why does red light refract the least in glass?

A

It is the fastest in glass

21
Q

Why does violet light refract the most in glass?

A

It is the slowest in glass

22
Q

What are the separated colours of white light called?

A

The visible spectrum

23
Q

Explain how total internal reflection is caused.

A

As the angle of incidence of a ray of light in glass increases, the internally reflected ray becomes stronger and the refracted ray becomes weaker.
Once the angle of refraction in air is 90 degrees, the critical angle has been reached and total internal reflection occurs beyond the critical angle.

24
Q

What is the critical angle of glass?

A

45 degrees

25
Q

Uses of total internal reflection

A
  1. Binoculars
  2. Optical fibres
  3. Endoscopes
26
Q

When light and water waves reflect….

A

Angle of incidence = angle of reflection
Reflected wavelength = incident wavelength
Reflected frequency = incident frequency
Reflected speed = incident speed.

27
Q

When light and water waves pass from air into glass/deep into shallow water…

A

They bend towards the normal
Refracted wavelength is less than incident wavelength
Refracted frequency = incident frequency
Refracted speed is less than incident speed

GCSE Physics Unit 2 (15 decks)

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