All about Light

Which of these is not a source of light?

• A candle flame

• The Sun

• The Moon

• A torch

Answer explanation

The Moon does not produce any light - it only reflects the light of the Sun

Imagine a candle flame. Light from the candle flame travels in which direction?

• In arcs

• In straight lines

• In random lines

• All of the above

Answer explanation

Light always travels in straight lines - we know this because a beam of light cannot curve around an object. If you hold a book between your eyes and the candle flame, you will not be able to see the flame - its light cannot travel through or around the bookLight always travels in straight lines - we know this because a beam of light cannot curve around an object. If you hold a book between your eyes and the candle flame, you will not be able to see the flame - its light cannot travel through or around the book

Approximately, how fast does light travel?

• 120 kilometres per hour

• 3,000 kilometres per hour

• 3,000 kilometres per second

• 300,000 kilometres per second

Answer explanation

Light travels faster than anything else - huge distances in space are described as 'light years'. Light travels the 150,000,000 kilometres from the Sun to the Earth in about eight minutes - can you imagine how far it could travel in a year?

Light travels slightly more slowly through air than through space. It is slowed down a little bit more by glass and which of the following?

• Metal

• Water

• Concrete

• Wood

Answer explanation

Metal, concrete and wood are opaque materials that do not transmit light (let light pass through them)

How will a beam of light shining on a glass prism behave?

• It will be refracted

• It will be completely reflected

• It will be completely absorbed

• It will not be changed at all, instead being perfectly transmitted

Answer explanation

When a beam of light shines on a glass prism, the light is refracted into its different colours, showing a 'rainbow' band of colours on the nearest white surfaces

If you half fill a clear glass with water and place a straw in the glass, how does the straw appear when you look at it carefully?

• It appears normal

• It seems to change colour

• It appears bent or broken

• It disappears completely

Answer explanation

This interesting effect is caused by the refraction of light in the water

There are forms of light which are invisible to the human eye. Which of these is an example?

• Ultraviolet

• Reflections

• Dark matter

• Starlight

Answer explanation

Ultraviolet (UV) light is visible to some insects and animals. Bumblebees can see UV light, for example

Visible light contains many colors. Which of the following is not one of these colors?

• Green

• Yellow

• Black

• Red

Answer explanation

Visible, or 'white' light does not include the colour black. The colours of visible light are those of the rainbow (red, orange, yellow, green, blue, indigo, violet). Objects look black when they absorb all of the light shining on them

Why does a green apple look green?

• It absorbs green light, but reflects the other colours

• It reflects green light but absorbs all of the other colors

• It absorbs green light

  but transmits all of the other colors

• It transmits all of the light

Answer explanation

The colour we see when we look at objects is the colour that is reflected by that object - all other colours are absorbed