Light And Sound

Question 1

What are sound waves?

Answer 1

Mechanical waves
Longitudinal
Produce same frequency of vibrations in air and in a solid

Question 2

How does hearing work?

Answer 2

Sound waves cause the ear drum to vibrate and the brain converts the vibrations within 20Hz to 20kHz
Higher frequency = higher pitch
Greater amplitude = louder sound
Hammer, anvil, stirrup amplify
Cochlea detects vibrations

Question 3

What are sound waves used for?

Answer 3

Ultrasound waves have a frequency above the range of human hearing
Ultrasound waves are always partially reflected when they meet a boundary
Can be used to measure distance in medical and industrial imaging
Echo is reflected sound wave
Echo sounding uses high frequency sound waves to measure depth of water and detect objects in deep water

Question 4

What are seismic waves?

Answer 4

Paths curve showing us there is gradual change in the density of the mantle
S waves are nor detected on the opposite side of the Earth so the outer core must be liquid
Kinks in the paths of P waves suggest a sudden change in density of material
Shadow zones where no P waves are detected suggest a solid inner core

Question 5

What are convex lenses?

Answer 5

Curve outwards
Make parallel rays converge at point
Focal length = distance from centre of lens to the principal focus where refracted rays of light come together

Question 6

What are images formed by convex lenses?

Answer 6

Real or virtual
Real images can be projected on to a screen
Virtual images appear to come from behind the lens

Question 7

What are concave lenses?

Answer 7

Curve inwards
They make parallel rays of light diverge

Question 8

How are images formed by concave lenses?

Answer 8

Virtual

Question 9

What can images formed by a lens be?

Answer 9

Magnified or diminished
Upright or inverted
Magnification = image height/ object height

Question 10

What is visible light?

Answer 10

Each colour within the visible light spectrum has its own narrow band of wavelength and frequency
Reflection from a smooth surface in a singular direction is specular reflection
A rough surface causes scattering of light ( diffuse reflection)

Question 11

How do coloured filters work?

Answer 11

Absorb certain wavelengths of light and transmitting others

Question 12

What is the different between transparent, translucent and opaque?

Answer 12

Transparent objects transmit visible light
Translucent objects transmit visible light but light rays are scattered or refracted inside them
Opaque objects do not transmit visible light but absorb and reflect it. The colour of an object depends on the wavelengths that they transmit and reflect

Question 13

Object at > 2f

Answer 13

Inverted, diminished, real
Eye/ camera

Question 14

Object at 2f

Answer 14

Inverted, same size, real

Question 15

Object at < 2f

Answer 15

Inverted, magnified, real
Projector

Question 16

Object at < f

Answer 16

Upright, magnified, virtual

Question 17

Focal ray

Answer 17

Passes through centre of lens with no change in direction

Question 18

Parallel

Answer 18

Passes through focal point after lens after travelling parallel to optical axis

Question 19

Focal ray

Answer 19

A ray that passes through the focal point emerges parallel to the optical axis on the other side

Question 20

When is a virtual image formed?

Answer 20

When imaginary rays intersect, not formed by real rays

Question 21

Red and blue

Answer 21

Magenta

Question 22

Green and blue

Answer 22

Cyan

Question 23

Red and green

Answer 23

Yellow

Question 24

Red, green and blue

Answer 24

White