Topic 6- Waves

Question 1

what do waves do?

Answer 1

• all waves transfer energy but they don’t transfer material

- waves reflect

Question 2

whats the definition of wave?

Answer 2

a wave is an oscillation in a medium

Question 3

define oscillation

Answer 3

vibration

Question 4

define medium

Answer 4

material that is vibrating

Question 5

transverse wave

Answer 5

medium vibrates at right angles to wave direction

e.g. light waves, waves on the surface of the sea

Question 6

longitudinal wave

Answer 6

medium vibrates parallel to wave direction

e.g. sound waves, ultrasound, pressure wave on a slinky

Question 7

define amplitude

Answer 7

the time taken for one whole wave to pass a point

Question 8

define wavelengh

Answer 8

the distance between two adjacent peaks or troughs (m)

Question 9

define frequancy

Answer 9

the number of waves passing a point each second (how frequently the waves pass) (Hz)

Question 10

define period

Answer 10

The time it takes for two successive wave crests to pass a given point. (s)

Question 11

define refraction

Answer 11

Refraction occurs when waves changes direction at a boundary, due to a change in speed

Question 12

define amplitude (sounds waves)

Answer 12

how loud or quiet it is (volume)

Question 13

what is the equation for wave speed and state the units

Answer 13

wave speed (metre per second) = frequency (hertz) × wavelength (metre)

Question 14

define crest

Answer 14

the highest point of the wave

Question 15

define trough

Answer 15

the lowest point of the wave

Question 16

define wave speed

Answer 16

the speed at which the wave travels (m/s)

Question 17

define wavelength/frequency (sound waves)

Answer 17

pitch - how high or low the sound is

Question 18

give the definition for echolocation and ultrasound

Answer 18

sound waves with frequency greater than 20000 Hz

Question 19

give an example of how echolocation can be used and state the equation than can be used

Answer 19

eg. In echolocation, bats send out short pulses that have a high frequency

distance to object = speed x time/2

Question 20

give example of ultrasound

Answer 20

eg. ultrasound probe - sends out pulses of ultrasound, which reflect off the baby. The echoes are used to build up the image.

Question 21

state the law of reflection ( light waves )

Answer 21

angle of incidence = angle of reflection

i = r

Question 22

state Snell’s Law ( refraction)

Answer 22

n (refractive index - how difficult a material is for light to get through) = sini/sinr

Question 23

explain total internal reflection and the critical (c) angle

Answer 23

when a light leaves a more dense material (eg. glass, water) it bends away from the normal. The maximum angle it can bend is 90 degrees.

Question 24

when does the ray totally internally reflect?

Answer 24

when the exiting ray hits at an angle greater than C it totally internally reflect

Question 25

what is the critical angle for glass?

Answer 25

approx 42 degrees

Question 26

Radio wave
wavelength
uses
dangers
detectors

Answer 26

• 1m to 1km
• communicative, radio TV
• none
• aeriel

Question 27

Microwaves
wavelength
uses
dangers
detectors

Answer 27

• 1mm-10cm
• heat food/cooking, satellite communication, SPS, phones, wireless rooter
• possibly heating
• aerial

Question 28

Infra-red
wavelength 
uses
dangers
detectors

Answer 28

• 10 ^-5m
• heaters, toasters, cooking, remote control, night vision
• burns
• skin (feel heat), digital camera

Question 29

Visible light 
wavelength
uses
dangers
detectors

Answer 29

• approx. 10^-1m
• seeing photography
• blidness
• eyes, photographic film, cameras

Question 30

Ultra violet
wavelength
uses
dangers
detectors

Answer 30

• approx. 10^-3m
• tanning beds, security/anti-forgery, sterilising, tanning
• excess exposure leads to skin cancer, blindness
• florescent, chemical, photography film

Question 31

X-rays
wavelength
uses
dangers
detectors

Answer 31

• approx. 10^-10m
• identify broken bones or damage to skeleton, medical imagery, metal detector
• cancer mutations
• photography film

Question 32

Gamma rays
wavelength
uses
dangers
detectors

Answer 32

• 10^-12m
• cancer treatment, sterilising medical equipment
• kill cells, cause cancer
• geiger counter