Light: Exams

Question 1

Name the 7 types of electromagnetic (EM) waves

Answer 1

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays

Question 2

Describe the relative wavelength and frequency of each type of EM wave

Answer 2

Highest frequency: Gamma rays
Highest energy: Gamma rays
Lowest frequency: Radio waves
Lowest energy: Radio waves

Question 3

Give example for the use of each type of EM wave

Answer 3

Radio waves – used for broadcasting radio and TV signals.
Microwaves – used for heating food in microwave ovens.
Infrared (IR) – used in remote controls and night vision cameras.
Visible light – lets us see and is used in lamps and torches.
Ultraviolet (UV) – used to sterilise equipment and kill germs.
X-rays – used to see inside the body for medical scans.
Gamma rays – used to treat cancer.

Question 4

What is the speed of light?

Answer 4

Approx 300,000 kilometres per second

Question 5

What is the law of reflection?

Answer 5

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

Question 6

Know the difference between regular and diffuse reflection.

Answer 6

Regular (Specular): Smooth surface, light reflects evenly, clear virtual image, angle in = angle out.

Diffuse: Rough surface, light scatters, no clear image, good for spreading light.

Question 7

Which colour has the shortest/longest wavelength

Answer 7

Longest wavelength: Red
Shortest wavelength: Violet

Question 8

What is lateral inversion

Answer 8

Lateral inversion is when an image in a mirror appears flipped sideways — left becomes right and right becomes left.
For example, when you raise your right hand, your mirror image looks like it’s raising its left hand.

Question 9

Explain how reflection of light determines an objects colour

Answer 9

• The colour we see depends on which colours of light are reflected from an object and which are absorbed.
• A red apple looks red because it reflects red light and absorbs all other colours
• A white object reflects all colours, and a black object absorbs all colours (reflecting none)
• So, the reflected light determines the colour that our eyes see.

Question 10

Images produced by mirrors eg by a plane, concave and convex mirror

Answer 10

• Plane mirror: Virtual, upright, same size, laterally inverted.
• Concave mirror: Can form real or virtual images — real ones are inverted, virtual ones are upright.
• Convex mirror: Always virtual, upright, and smaller than the object.

Question 11

Give common examples for the use of concave and convex mirrors

Answer 11

Concave mirrors (curved inwards):
-makeup mirrors – they magnify your face.
-Dentist mirrors – to see enlarged images inside the mouth.

Convex mirrors (curved outwards):
- Vehicle side mirrors – give a wider view of traffic behind.
- Security mirrors – in shops or driveways to see around corners.

Question 12

What is the rule of refraction?

Answer 12

When light enters a denser medium (like air → glass or air → water), it bends towards the normal.
When light enters a less dense medium (like glass → air), it bends away from the normal.

Question 13

What is a biconvex, biconcave, converging and diverging lens?

Answer 13

Biconvex lens: Curved outwards on both sides, brings light rays together (converges).
Biconcave lens: Curved inwards on both sides, makes light rays spread out (diverges).
Converging lens: Same as a convex lens — focuses light to a point.
Diverging lens: Same as a concave lens — spreads light out.

Question 14

How does light bend through various lenses?

Answer 14

Converging Lens (Convex)
- How light bends: Parallel light rays bend inward toward the center of the lens.
- Focal point (F): The point on the opposite side of the lens where all the rays meet.
- Example: A flashlight beam focused to a point.
2. Diverging Lens (Concave)
- How light bends: Parallel light rays bend outward away from the center of the lens.
- Focal point (F): The point on the same side as the incoming light from which the rays appear to come.
- Example: Light spreading out from a peephole lens.

Question 15

Images produced by lenses eg real, virtual, inverted, upright images

Answer 15

Convex (converging) lens:
- Object far → real, inverted, smaller
- Object close → virtual, upright, larger
Concave (diverging) lens:
- Always virtual, upright, smaller

Question 16

Refraction in a pool of water

Answer 16

• When light passes from air into water, it bends (refracts) because it slows down in the denser water.
• This makes objects under the water — like a coin or your legs — look closer to the surface than they really are

Question 17

Dispersion of white light ROY G BIV

Answer 17

• Dispersion is when white light splits into its seven colours — Red, Orange, Yellow, Green, Blue, Indigo, Violet — as it passes through a prism or raindrop.
• This happens because each colour bends by a different amount, with red bending the least and violet the most.

Question 18

How do we see things?

Answer 18

We see things because light reflects from objects and enters our eyes.
Our eyes’ lenses focus the light onto the retina, which sends signals to the brain — that’s how we recognise shapes, colours, and movement.

Question 19

Why do we see colour/brightness? Rod, cones etc

Answer 19

We see colour because objects absorb some colours of light and reflect others. The reflected light enters our eyes, and our brain interprets it as the object’s colour. For example, a red apple reflects red light and absorbs the rest.

Question 20

How does the eye work?

Answer 20

• Cornea – Clear window at the front; bends (refracts) light to help focus it.
• Pupil – Hole in the iris; light enters through here.
• Iris – Coloured part; changes size to control light.
• Lens – Focuses light on the retina; shape changes with ciliary muscles.
• Retina – Back layer with rods & cones; turns light into signals.
• Optical Nerve – Carries messages from the retina to the brain.
• Sclera – Tough white outer layer; protects the eye.
• Vitreous Humour – Jelly inside; keeps shape and lets light travel.

Question 21

What role does the eye play in sight?

Answer 21

• The eye works like a camera — it collects light, focuses it, and sends messages to the brain.
  – Light enters through the cornea and pupil.
  – The lens focuses the light onto the retina at the back of the eye.
  – The retina changes the light into electrical signals, which travel through the optic nerve to the brain, where the image is formed.

Question 22

What parts of the eye will a light ray pass through to strike the retina?

Answer 22

the cornea, the pupil, the lens, and the vitreous humor

Question 23

Be able to name and describe 2 vision defects

Answer 23

Short-sightedness (Myopia)
- You can see near objects clearly, but distant objects look blurry.

Long-sightedness (Hyperopia)
- You can see distant objects clearly, but near objects are blurry.

Question 24

diagram of a wave includes:

Answer 24

wavelength, amplitude, frequency, crest and trough.

Question 25

At what speed do the various energy levels of the electromagnetic spectrum travel?

Answer 25

They travel at the same speed (the speed of light)

Question 26

Describe how the path of light changes when it passes through different transparent media.

Answer 26

More dense moves Towards the normal Less dense moves Away from the normal

Question 27

What is a converging and diverging lens?

Answer 27

Converging Lens (Convex) Diverging Lens (Concave) Converging: What it does: Brings light rays together to a point (focal point). Diverging: What it does: Spreads light rays apart, as if coming from a point.

Question 28

What are real and virtual images?

Answer 28

Real image: - What it is: An image that can be projected onto a screen. - How it forms: Light rays actually meet at a point after reflecting off a mirror or passing through a lens. Virtual image: - What it is: An image that cannot be projected onto a screen. - How it forms: Light rays don’t actually meet; they only appear to come from a point.

Question 29

Explain how we see colour.

Answer 29

We see colour because objects absorb some colours of light and reflect others. The reflected light enters our eyes, and our brain interprets it as the object’s colour. For example, a red apple reflects red light and absorbs the rest.

Question 30

How does the eye change in bright light or darkness? Explain why this occurs and which parts of the eye are involved.

Answer 30

- In bright light, the pupil gets smaller (contracts) to reduce the amount of light entering the eye. This protects the retina from too much light. - In darkness, the pupil gets bigger (dilates) to let in more light, helping you see better.

Question 31

3. The image formed by a biconvex lens is best described as: a. Virtual b. Virtual if the object is closer than the focal point and real if the object if further than focal point c. Real d. Neither virtual nor real

Answer 31

B. Virtual if the object is closer than the focal point and real if the object if further than focal point

Question 32

The wavelength of waves could be measured in:

Answer 32

Meters

Question 33

The image in a plane mirror is always: a. virtual, upright and the same size b. real, upright and the same size c. virtual, upright and smaller d. real, upright and smaller

Answer 33

a. virtual, upright and the same size

Question 34

The eye contains rod cells that are located in the: a. Iris and help to detect the brightness of light b. Iris and help to detect the colour of light c. Retina and help to detect the brightness of light d. Retina and help to detect the colour of light.

Answer 34

c. Retina and help to detect the brightness of light