Topic 6 - Waves (2)

Question 1

LENSES:
How do lenses form images?

Answer 1

by refracting light and changing its direction

Question 2

LENSES:
What are the two types of lenses?

Answer 2

• convex and concave
  (they are different shapes and have opposit effects on light rays)

Question 3

LENSES:
How is a convex lens shaped?
What effect does it have on light rays?

Answer 3

• bulges outwards
• causes light rays parallel to the axis to be brought together (converge) at the principal focus

Question 4

LENSES:
How is a concave lens shaped?
What effect does it have on light rays?

Answer 4

• caves inwards
• causes parallel light rays to spread out (diverge)

Question 5

LENSES:
What is the axis of a lens?

Answer 5

the line passing through the middle of a lens

Question 6

LENSES:
What is the principal focus of a convex lens?

Answer 6

where rays hitting the lens parallel to the axis meet

Question 7

LENSES:
What is the principal focus of a concave lens?

Answer 7

the point where rays hitting the lens parallel to the axis appear to all come from - you can trace them back until they all appear to meet up at a point behind the lens

Question 8

LENSES:
What side(s) of the lens is the principal focus?

Answer 8

there is a principal focus on each side of the lens

Question 9

LENSES:
What is the focal length?

Answer 9

the distance from the centre of the lens to the principal focus

Question 10

LENSES:
What is the distance from the centre of the lens to the principal focus called?

Answer 10

the focal length

Question 11

LENSES:
What are convex lenses also called?

Answer 11

converging lenses

Question 12

LENSES:
What are concave lenses also called?

Answer 12

diverging lenses

Question 13

LENSES:
What are the three rules for refraction in a convex lens?

Answer 13

• an incident ray parallel to the axis refracts through the lens and passed through the principal focus on the other side
• an incident ray passing through the principal focus refracts through the lens and travels parallel to the axis
• an incident ray passing through the centre of the lens carries on in the same direction

Question 14

LENSES:
What are the three rules for refraction in a concave lens?

Answer 14

• an incident ray parallel to the axis refracts through the lens, and travels in line with the principal focus (so it appears to have come from the principal focus)
• an incident ray passing through the lens towards the principal focus refracts through the lens and travels parallel to the axis
• an incident ray passing through the centre of the lens carries on in the same direction

Question 15

VISIBLE LIGHT:
What is the name of the spectrum of EM waves can we see?

Answer 15

the visible light spectrum

Question 16

VISIBLE LIGHT:
What is the visible light spectrum?

Answer 16

a range of wavelengths that we percievd as different colours

Question 17

VISIBLE LIGHT:
What is the difference between differnt colours?

Answer 17

each colour has it own narrow range of wavelengths

Question 18

VISIBLE LIGHT:
What are the primary colours of light?

Answer 18

pure red, green and blue

Question 19

VISIBLE LIGHT:
What are the only colours you can’t make by mixing?

Answer 19

the primary colours (red, green, blue)

Question 20

VISIBLE LIGHT:
What do you get when all the primary colours are put together?

Answer 20

white light

Question 21

VISIBLE LIGHT:
What does the colour and transparency of an object depend on?

Answer 21

how the object absorbs, transmits and reflects different wavelengths of light

Question 22

VISIBLE LIGHT:
What are opaque objects?
What happens to the wavelengths that hit them?

Answer 22

• objects that do not transmit light
• they abosrb some wavelengths of visible light waves and reflect others

Question 23

VISIBLE LIGHT:
What does the colour of an opaque object depend on?

Answer 23

which wavelengths of light are most strongly reflected

Question 24

VISIBLE LIGHT:
Why does a red apple appear red?

Answer 24

the wavelengths corresponding to the red parts of the visible spectrum are most strongly reflected - the other wavelengths of light are absorbed.

Question 25

VISIBLE LIGHT: In what 2 ways can opaque objects that aren't primary colours reflect light?

Answer 25

- reflect wavelengths of light corresponding to that colour - OR the wavelengths of the primary colours that can mix together to make that colour

Question 26

VISIBLE LIGHT: In what 2 ways can a banana appear yellow?

Answer 26

- either it's reflecting yellow light - OR because its reflecting both red and green light

Question 27

VISIBLE LIGHT: How do white objects appear white?

Answer 27

reflect all the wavelengths of visible light equally

Question 28

VISIBLE LIGHT: How do black objects appear black?

Answer 28

they absorb all wavelengths of visible light (your eyes see black as a lack of any visible light - colour)

Question 29

VISIBLE LIGHT: How do objects appear transparent or translucent?

Answer 29

- they transmit light (not all light that hits the surface is absorbed or reflected - some can pass through)

Question 30

VISIBLE LIGHT: What determines the colour of a transparent or translucent object?

Answer 30

the wavelengths of light transmitted and reflected by it

Question 31

VISIBLE LIGHT: What do colour filters do?

Answer 31

they filter out different wavelengths of light - only certain colours (wavelengths) are transmitted - the rest are absorbed

Question 32

VISIBLE LIGHT: What does a primary colour filter do?

Answer 32

- only transmits that colour (if white light is shone at a blue colour filter, only blue light will be let through - the rest is absorbed)

Question 33

VISIBLE LIGHT: How does a blue object appear through a blue colour filter? Why?

Answer 33

- it will still look blue - blue light is reflected from the object's surface and is transmitted by the filter

Question 34

VISIBLE LIGHT: How would a red (or any colour not made from blue light) object appear through a blue filter? Why?

Answer 34

- it would appear black - all of the light reflected by the object will be absorbed by the filter

Question 35

VISIBLE LIGHT: What do filters that aren't for primary colours let through?

Answer 35

both the wavelengths of light for that colour AND the wavelengths of the primary colours that can be added together to make that colour