4.1 Waves and vibrations

Question 1

How are sound waves created

Answer 1

Making a surface vibrate so it sends compression waves through the surrounding air

Question 2

Examples of waves that pass through a substance

Answer 2

Sound waves
Seismic waves
Waves on strings

Question 3

What name is given to waves that pass through a substance

Answer 3

Mechanical waves

Question 4

How do waves pass through a substance

Answer 4

When waves pass through a substance, the particles of the substance vibrate in a certain way which makes nearby particles vibrate in the same way and so on

Question 5

What are electromagnetic waves

Answer 5

Oscillating electric and magnetic fields that progress through space without the need for a substance
The vibrating electric field generates a vibrating magnetic field, which generates a vibrating electric field further away and so on

Question 6

Examples of electromagnetic waves

Answer 6

Radio waves
Microwaves
Infrared radiation
Light
Ultraviolet radiation
X-rays
Gamma radiation

Question 7

What are longitudinal waves

Answer 7

Waves in which the direction of vibration of the particles is parallel to the direction in which the wave travels

Question 8

Examples of longitudinal waves

Answer 8

Sound waves
Primary seismic waves
Compression waves on a slinky

Question 9

What are transverse waves

Answer 9

Waves in which the direction of vibration is perpendicular to the direction of in which the wave travels

Question 10

Examples of transverse waves

Answer 10

Electromagnetic waves
Secondary seismic waves
Waves on a string or wire

Question 11

In what case are transverse waves plane-polarised

Answer 11

If the vibrations stay in one plane only

Question 12

Sources of unpolarised light

Answer 12

Filament lamp

Candle

Question 13

What happens if unpolarised light is passed through a polaroid filter

Answer 13

The transmitted light is polarised as the filter only allows through the light which vibrates in a certain direction, according to the alignment of its molecules

Question 14

What happens if unpolarised light is passed through two polaroid filters

Answer 14

The transmitted light intensity changes if one polaroid is turned relative to the other one. The filters are said to be crossed when the transmitted intensity is a minimum. At this position, the polarised light from the first filter cannot pass through the second filter, as the alignment molecules in the second filter is perpendicular to the alignment in the first.

Question 15

What is the plane of polarisation of an electromagnetic wave defined as

Answer 15

The plane in which the electric field oscillates

Question 16

What do polaroid sunglasses help with

Answer 16

Reducing the glare of light reflected by water or glass

The reflected light is polarised and the intensity is reduced when it passes through the polaroid sunglasses

Question 17

Radio waves from a transmitter are ______. The aerial of a radio receiver needs to be ______ in the same ______ as the radio waves to obtain the best ______.

Answer 17

Polarised
Aligned
Plane
Reception