Colour (Light)

Question 1

What is white light made of?

Answer 1

All the colours of the visible spectrum mixed together.

Question 2

What happens when white light hits a red object?

Answer 2

The red object reflects red light and absorbs all the other colours.

Question 3

What are the primary colours of light?

Answer 3

Red, green, and blue.

Question 4

What colour do you see when all three primary colours mix?

Answer 4

White.

Question 5

What is refraction?

Answer 5

When light bends as it passes from one material to another (like air to glass).

Question 6

Why does refraction happen?

Answer 6

Because light travels at different speeds in different materials.

Question 7

What happens when light enters a denser material (like air → glass)?

Answer 7

It slows down and bends towards the normal.

Question 8

What happens when light leaves a denser material?

Answer 8

It speeds up and bends away from the normal.

Question 9

What is the electromagnetic spectrum?

Answer 9

A range of waves that all travel at the same speed in a vacuum but have different wavelengths and frequencies.

Question 10

Name the electromagnetic spectrum in order from longest to shortest wavelength.

Answer 10

Radio, microwave, infrared, visible, ultraviolet, X-rays, gamma rays.

Question 11

Which EM waves are used in mobile phones?

Answer 11

Microwaves.

Question 12

Which EM waves can cause sunburn?

Answer 12

Ultraviolet (UV) rays.

Question 13

What is wavelength?

Answer 13

The distance from one wave peak to the next.

Question 14

What is frequency?

Answer 14

The number of waves that pass a point per second. Measured in hertz (Hz).

Question 15

What is wave speed?

Answer 15

How fast the wave moves — calculated with:
wave speed = frequency × wavelength

Question 16

What is the law of reflection?

Answer 16

The angle of incidence = angle of reflection.

Question 17

What type of surface gives a clear reflection?

Answer 17

A smooth, shiny surface (like a mirror)

Question 18

What is the difference between specular reflection and diffuse scattering?

Answer 18

Specular: smooth surface, light reflects in one direction.

Diffuse: rough surface, light reflects in many directions.

Question 19

Does diffuse scattering break the law of reflection? Explain.

Answer 19

No — each ray still reflects with angle in = angle out, but the rough surface means rays reflect in different directions, so it appears scattered.

Question 20

Why can you see yourself in a mirror but not on a wooden table?

Answer 20

Mirror = smooth → specular reflection (clear image).

Wood = rough → diffuse reflection (no image).

Question 21

Light bends towards the normal when moving into a ________ material.

Answer 21

Denser

Question 22

A ray of light hits glass head-on (at 90°). Will it bend?

Answer 22

No — it will slow down, but not bend.