waves and waves properties

Question 1

What is a wave?

Answer 1

Particles that make up a wave OSCILLATE (vibrate) about a fixed point. All waves transfer energy from one another

Question 2

What is a period?

Answer 2

PERIOD-time taken for one wave to pass a point

PERIOD=1/FREQUENCY units are seconds

Question 3

Why does frequency not change?

Answer 3

wave speed=frequency x wavelength
Frequency doesn’t not change because the same number of waves are being produced
the speed and wavelength are directly proportional

Question 4

What happens in reflection?

Answer 4

when a wave reaches a boundary between one medium (material) they can be reflected, refracted, absorbed or transmitted

Question 5

What is Refraction?

Answer 5

waves can change direction when they pass from one material to another this depends on the angle and the materials involved.

Question 6

How does sound waves work?

Answer 6

sound waves in air can trigger vibrations in solid. This only works for a limited range of frequencies. Normal human hearing is 20hz-20000hz and frequencies outside of this range may not cause the ear drum to vibrate

Question 7

How does ultrasound work?

Answer 7

ultrasonic waves have a frequency over 20MHz so they cannot be heard by humans
When an ultrasonic wave meets a boundary between 2 different medias it is partially reflected

Question 8

What is echo sounding?

Answer 8

echo sounding or sonar is the use of ultrasonic waves for detecting objects in deep water and measuring the depth of the water
This involves sending an ultrasound pulse into the water which reflects back when it hits a surface
DISTANCE=SPEED X TIME

Question 9

What two seismic waves are produces in an earthquake?

Answer 9

P-WAVES AND S-WAVES

Question 10

What happens during an earthquake?

Answer 10

-seismic waves travel outwards from the earthquake and are capable of travelling all the way through the earth
-Seismic waves travel in a curved path due to density density changes in the earth
-Detectors are placed around the earth to measure where and when the different waves arrive
-

Question 11

What are S-Waves shadow Zones?

Answer 11

• There are large parts of the earth where s-waves are not detected because s-waves cannot pass through a liquid.
• This means the earth must contain a liquid core

Question 12

How do you carry out the practical for reflection and refraction?

Answer 12

1) Draw around the semi circular block
2) Mark the position of the light ray at the start and end were it enters and exits the block
3) Remove the block and connect the marks to show the light rays
4) Add normal lines and measure angle of incidence and angle of refraction
5) Repeat for a range of incident angles and use different materials

Question 13

What is white light?

Answer 13

• White light is a mixture of different colours

* Has its own narrow band of frequency and wavelength

Question 14

What is a transverse wave?

Answer 14

oscillations are perpendicular(up and down) to the direction of energy transfers(sideways)(EG. ripples on the surface of water)

Question 15

What is a longitudinal wave?

Answer 15

• oscillations are parallel to the direction of energy transfers.(EG. sound waves)
• They need a medium to travel in such as air, solid or liquid

Question 16

What is the difference between frequency and amplitude?

Answer 16

FREQUENCY-number of waves passing a fixed point per second measured in Hz
AMPLITUDE-the maximum displacement that any particles achieve from its undisturbed position in metres

Question 17

What is the wavelength?

Answer 17

WAVELENGTH-distance from one point of a wave to the equivalent point on the next wave in metres

Question 18

What indicates the amount of energy?

Answer 18

amplitude indicates the amount of energy a wave is carrying the more energy the more the amplitude

Question 19

What is wave speed?

Answer 19

wave speed is the speed at which the wave moves through the medium
As waves are transmitted their speed and wavelength changes

Question 20

What happens when waves are reflected?

Answer 20

when waves are reflected at a surface the angle of incidence is equal to the angle of reflection.

Question 21

What causes refraction?

Answer 21

Refraction is due to the difference in the wave speed in different media

Question 22

What happens when a light wave enters at an angle in a medium which it travels slow?

Answer 22

• the first part to enter the medium slows down
• the rest of the wave continues at a higher speed
• this causes the wave to change direction

Question 23

How does sound work in the ear?

Answer 23

sound waves in the air are funnelled into the ear where they hit the ear drum(thin membrane) the sound waves causes the ear drum and inner ear to vibrate. This causes sound.

Question 24

What are the properties of sound?

Answer 24

-high frequency high pitch, low frequency low pitch, small amplitude quite sound, large amplitude loud sound

Question 25

What can/cant’t a sound wave move through?

Answer 25

sound waves can only move through a medium, they cannot move through a vacuum because there’s no particles and sound waves can be reflected.

Question 26

What is sound and what does it have?

Answer 26

have frequency, amplitude and wavelength. sound is a longitudinal wave

Question 27

Why are ultrasound used?

Answer 27

to detect defeats in objects without opening them(this works for organs that is not surrounded by bone EG. KIDNEY) they are also used in pre-natal scanning
does not cause mutations

Question 28

What are P-Waves?

Answer 28

• longitudinal wave
• travel at the speed of sound faster then s-waves
• Travel through solids and liquids

Question 29

What are S-Waves?

Answer 29

• Transverse waves

- not able to travel through liquids, but can travel through solids

Question 30

What is the P-Wave shadow zone?

Answer 30

–p-wave shadow zones are due to the fact p-waves travel faster in solids then liquids, this means p-waves slow down as they enter the liquid core

Question 31

How does a P-Wave confirm the outer core is a liquid?

Answer 31

-they then change direction (refract) and also change direction when they leave the outer core

Question 32

What are the variables for the practical?

Answer 32

CV-material the block is made from
IV-angle of incidence
DV-angle of refraction

Question 33

How does a colour filter work?

Answer 33

*Colour filters work by absorbing specific wavelength
and transmitting other wavelengths
*If all waves reflect equally the object appears white
and if absorbed the object appears black

Question 34

What happens if the filter and object is the same colour/How is the colour black and red produced?

Answer 34

object and filter same- it will appear its true colours
*if the object is diff to it to the filter a few things can happen; red+blue stripped object + red filter=red+black
green object(absorbs the red) +red filter=black (reflects no light)