Waves

Question 1

What are waves and what do they do?

Answer 1

Transfer energy from one place to another
Transfer information
There are different types of waves

Question 2

What are the different types of waves?

Answer 2

Sound waves, Water waves, Springs and Earthquakes are all examples of Mechanical waves which are vibrations that can travel through a medium
Light waves, Radio waves and Microwaves are examples of electromagnetic waves which can travel through a vacuum

Question 3

What are longitudinal waves?

Answer 3

Vibrate parallel to direction of energy transfer of the waves
Eg sound
When an object vibrates in air it makes the air around it vibrate as it pushes and pulls on the air - the oscillation is the sound waves

Question 4

What are transverse waves?

Answer 4

Vibrate perpendicular (at right angles) to direction waves transfer energy
Eg light
All electromagnetic waves are transverse
Mechanical waves can be transverse or longitudinal - water waves are transverse

Question 5

How do we measure waves?

Answer 5

1. Amplitude - height of wave above position of rest
2. Wavelength - lambda - distance between two corresponding points on waves usually trough or peak = metres
3. Frequency - how many waves pass by a point every second - hertz

Question 6

What is the wave equation?

Answer 6

Relates speed of wave to its frequency and wavelength 
Wave speed (m/s) = frequency (Hz) x wavelength (m)
V = f x ¥

Question 7

What is the equation for period?

Answer 7

Period = 1➗frequency
T= 1➗f

Question 8

What is reflection?

Answer 8

All waves can be reflected
Reflection occurs when a wave changes direction at a boundary between two different mediums
When reflected waves always obey law of reflection
All angles measured to the normal

Question 9

What happens when plane waves reflect off a surface?

Answer 9

Frequency and wavelength remain unchanged

Question 10

What is refraction?

Answer 10

Refraction occurs when wave changes direction as its speed changes
When a wave refracts there is always some reflection
Slowing down it refracts towards the normal
Speeding up it refracts away from the normal
Water waves refract when a change in depth

Question 11

What is the law of reflection?

Answer 11

Angle of incidence = angle of reflection

I=r

Question 12

Explain the electromagnetic spectrum?

Answer 12

Electromagnetic spectrums are electric and magnetic disturbances that transfer energy from one place to another
Energy transferred depends on wavelength of waves
Long - radio waves- as long as 10km
Short - x rays and gamma rays - 0.000000000001mm

Question 13

The speed of electromagnetic waves?

Answer 13

Travel at speed of light: 3000000 m/s

Question 14

What is the frequency of mobile phone waves?

Answer 14

900 million Hz

Question 15

Examples of wavelength?

Answer 15

Radio - wavelength 10(3) - size of buildings - frequency 10(4)-(8) - temperature 0->0.5k
Microwave - 10(-2) - honey bee - 10(8)-(12) - 0.5->1k
Infra red - 10(-5) - pinpoint - 10(12) - 1->100k
Visible - 0.5 x 10(-6) - bacteria, protozoan - 10(15) - 100->10000k
Ultra violet - 10(-8) - molecules - 10(16) - 10000->5 millionk
X-ray - 10(-10) - atoms - 10(18) - 5->10 millionk
Gamma rays - 10(-12) - atomic nuclei - 10(20) - 10 millionk+

Question 16

Details of Radio waves?

Answer 16

Uses - communications and transmissions
Medicine - communications
Dangers - cancer and other health problems
Detectors - aerials

Question 17

Details of Microwaves?

Answer 17

Uses - Cookers, mobile phones, speed cameras, transmitter towers
Medicine - communications
Dangers - cataracts in eyes, brain damage, cooked by radar
Detectors - aerials

Question 18

Details of Infrared waves?

Answer 18

Uses - tracking criminals, remote controls, night sights for weapons, alarm systems
Danger - overheating
Detectors - infrared cameras and infrared detectors

Question 19

Details of Visible light waves?

Answer 19

Uses - to see things, laser in compact disc player, laser printers, aircraft aiming systems
Dangers - eye damage in retina
Detectors - eyes and glass prisms to see all colours of light

Question 20

Details of Ultra violet waves?

Answer 20

Use - sun tan, detecting forged bank notes, security marker pens
Medical - hardening dental filling, kills microbes, sterilise equipment and can produce vitamin D
Danger - damage in retina and sun burn
Detectors - special film

Question 21

Details of X-ray waves?

Answer 21

Uses - airport security checks and astronomers using radio telescopes to see X-ray in space
Medical - sees through soft tissue to make radiograph, low energy X-ray scan soft areas eg brain and barium sulphate absorbs X-rays to allow intestine view
Danger - cell damage and cancer
Detectors - special film forms a radio graph

Question 22

Details of Gamma ray waves?

Answer 22

Uses - high frequency so carries large amount of energy and lead or concrete can block it
Medical - radiotherapy kills rapidly dividing cancer cells and traces to view inside body
Danger - ionisation in tissue and cancer
Detectors - Geiger counter or photographic film