7.1 How Do We See Things?

Question 1

What is light?

Answer 1

Light is a form of energy helps us see things. It travels in a straight line and has a dual nature. It does not need a medium to travel through.

A dual nature means that light can travel in waves or has a particle like behavior, which means it has the energy to set stationary objects into motion.

Question 2

What are luminous objects?

Answer 2

Luminous objects produce their own light.
E.g., sun, light bulbs, florescent lights

Question 3

What are non-luminous objects?

Answer 3

Non-luminous objects are man-made or natural and do not have their own source of light. There are two types - point and extended.
E.g., Moon, Earth, Chairs, etc.

Question 4

How do we see luminous and non-luminous objects?

Answer 4

Luminous objects produce their own light so hence we can see them. Non-luminous objects reflect the light of luminous objects and hence we can see them.

Question 5

What can happen to light once it hits an object?

Answer 5

Light can be transmitted by (pass through) the object it hits or reflected (turned back) or absorbed.

Question 6

What happens after an object absorbs light?

Answer 6

Light that is absorbed is neither transmitted nor reflected, it stays inside the object. However, the energy can’t simply disappear, so the energy of the light is transferred into thermal energy.

Question 7

Name the three types of material which light interact with.

Answer 7

1. Opaque - light cannot pass through - mainly reflection, then absorption
   E.g., bricks
2. Translucent - some light can pass through - mainly transmission then absorption
   E.g., stained or frosted glass, tracing or butter paper
3. Transparent - all light passes through - mainly transmission
   E.g., glass windows