Waves

Question 1

In longitudinal waves, is energy transferred parallel or perpendicular to the direction of the vibrations?

Answer 1

Parallel

Question 2

In transverse waves, is energy transferred parallel or perpendicular to the vibrations?

Answer 2

Perpendicular

Question 3

How is the wavelength measured in longitudinal waves?

Answer 3

From the center of one compression/rarefaction to the center of the next.

Question 4

What is the amplitude of a wave?

Answer 4

The distance from the equilibrium position to the crest.

Question 5

Are EM waves transverse or longitudinal?

Answer 5

Transverse.

Question 6

Are sound waves transverse or longitudinal?

Answer 6

Longitudinal.

Question 7

What is the difference between mechanical waves and electromagnetic waves?

Answer 7

EM waves can travel through a vacuum, but mechanical weaves have to travel through a medium.

Question 8

What is the frequency?

Answer 8

The number of waves that pass a point in one second.

Question 9

What is the time period?

Answer 9

The time taken for one complete wave cycle.

Question 10

What is the speed of light?

Answer 10

3x10⁸ m/s
300,000,000 m/s

Question 11

Why are waves refracted when they hit the boundary of a material at an angle?

Answer 11

• Speed of waves is different in materials with different densities
• Part of the wave hits the boundary between materials first
• Its wavelength increases/decreases and the speed changes
• This changes the direction of the wave

Question 12

Why are water waves refracted?

Answer 12

They travel slower in shallower water.

Question 13

What is diffraction?

Answer 13

The spreading out of waves through a gap or around an obstacle.

Question 14

When do you get the best diffraction?

Answer 14

When the wavelength is a similar size to the gap it is going through.

Question 15

Why is range of hearing limited?

Answer 15

Converting sound into vibrations through solids only works for a limited frequency range.

Question 16

What is the auditory range of humans?

Answer 16

20-20,000Hz

Question 17

How does ultrasound scanning work?

Answer 17

• The waves are partially reflected different amounts by different mediums.
• The reflected waves are detected by a receiver.

Question 18

Are P-waves longitudinal or transverse?

Answer 18

Longitudinal
They travel faster in solids than liquids.

Question 19

Are S-waves longitudinal or transverse?

Answer 19

Transverse
Only travel through solids.

Question 20

Which is more destructive: P-waves or S-waves?

Answer 20

S-waves
They shave building horizontally causing a lot of damge.

Question 21

Why do waves change direction as they pass through the mantle?

Answer 21

There is a gradual change in density.

Question 22

What happens to waves at boundarys between the earths layers?

Answer 22

• The waves are refracted.
• There is a large change in density.

Question 23

What is an S-wave shadow?

Answer 23

The area that receives no S-waves as they are blocked by the liquid outer core.

Question 24

What are the Em waves in order?

Answer 24

Radio
Microwave
Infra-red
Visible light
Ultra-violet
X-rays
Gamma

Question 25

Which of the Em waves has the largest wavelength?

Answer 25

Radio waves.

Question 26

Which of the Em waves has the most energy?

Answer 26

Gamma.

Question 27

Which of the Em waves has the largest frequency?

Answer 27

Gamma.

Question 28

Which 3 types of wave are ionising?

Answer 28

- UV - X-rays - Gamma

Question 29

How are radio waves produced?

Answer 29

Oscillations in electrical circuits.

Question 30

What happens when radio waves are absorbed by an electrical circuit?

Answer 30

They induce an alternating current with the same frequency as the wave

Question 31

What are **radio waves** used for and why?

Answer 31

**TV and radio transitions** - Large wavelengths (refract around large objects) - Reflected by the ionosphere (travel long distances)

Question 32

What are **microwaves** used for and why?

Answer 32

**Microwaves and satellite communication** - Travel through the ionosphere - Absorbed by water molecules

Question 33

What are the dangers of **microwaves**?

Answer 33

Internal tissue heating.

Question 34

What are **infra-red waves** used for and why?

Answer 34

**Remote controls, heating, night vision** - Warm objects give out more infra-red radiation

Question 35

What are the dangers of **infra-red waves**?

Answer 35

Skin burns.

Question 36

What are **visible light waves** used for?

Answer 36

Endoscopes (devices that look inside the body) and fiber-optic communication

Question 37

What are the dangers of **visible light waves**?

Answer 37

Blindness.

Question 38

What are **ultraviolet waves** used for?

Answer 38

**Security markings on bank notes**

Question 39

What are the dangers of **ultraviolet waves**?

Answer 39

Burns and cancer (ionising radiation).

Question 40

What are **X-ray waves** used for and why?

Answer 40

**medical scanning** - Absorbed only be denser structures - Show up on film or charge-couple device (CCD)

Question 41

What are the dangers of **X-ray waves**?

Answer 41

Cancer (ionising radiation).

Question 42

What are **gamma waves** used for and why?

Answer 42

**Sterilization and radiotherapy** - The most ionising of the EM waves

Question 43

What is the name for reflection in a smooth surface?

Answer 43

Specular reflection

Question 44

What is the name for reflection in a rough surface?

Answer 44

Diffuse reflection

Question 45

Which direction does light bend when entering **more dense** material?

Answer 45

Towards the normal.

Question 46

Which direction does light bend when entering **less dense** material?

Answer 46

Away from the normal.

Question 47

What colour light do red objects reflect?

Answer 47

Red light, they absorb all other colours.

Question 48

How do coloured filters work?

Answer 48

They only let through some colours of light.

Question 49

What is a perfect black body?

Answer 49

An object that absorbs all radiation incident on it. It is the best possible emitter.

Question 50

What do hotter objects emmit?

Answer 50

Shorter wavelengths.

Question 51

How does a light bulb work?

Answer 51

- Current flows through the filament - Filament heats up - Thermal emission moves into the visible spectrum

Question 52

How does the greenhouse effect work?

Answer 52

- Infrared radiation from the sun warms the ground - The ground emits longer-wavelength infrared - CO₂ molecules absorb and re-emit the long-wavelength infrared

Question 53

What are convex lenses?

Answer 53

Converging lenses

Question 54

What are concave lenses?

Answer 54

Diverging lenses