3 Waves

Question 1

Waves transfer energy …

Answer 1

without a transfer of matter

Question 2

Transverse

Travsverse waves have vibrations that are …

Answer 2

parallel to the direction of the wave

Question 3

Give 3 examples of:

Transverse waves

Answer 3

Light - EM Spectrum
Water
Secondary seismic waves

Question 4

Longitudinal

Longitudinal waves have oscillations that are…

Answer 4

parallel to the direction of the wave

Question 5

Give 2 examples of:

Longitudinal waves

Answer 5

Sound

Primary seismic waves

Question 6

Define:

Amplitude

Answer 6

The maximum displacement of any particle/wave from its undisturbed position (equilibrium)

Question 7

WAVES

Question 8

difference between longitudinal and transverse waves

Answer 8

transverse = wave that vibrates perpendicular to the direction of the oscillation
e.g. light (EM Spectrum)
longitudinal = wave that vibrates parallel to the direction of the oscillation
e.g. sound

Question 9

define wavefront

Answer 9

2 or more waves moving together have wavefronts, imaginary planes connect points on adjacent waves, vibrate together

Question 10

define amplitude

Answer 10

maximum displacement of particles from their equilibrium position.

Question 11

define wavelength

Answer 11

distance between a particular point on one cycle of the wave and the same point on the next cycle.

Question 12

define frequency

Answer 12

number of waves passing a particular point per second. Is measured in Hertz (Hz).

Question 13

define time period

Answer 13

time it takes for one complete wave to pass a particular point

Question 14

waves transfer energy and information without transferring _______

Answer 14

matter

Question 15

wavespeed =

Answer 15

wavelength x frequency
v = lamda x f
m/s = Hz x m

Question 16

frequency =

Answer 16

1/time period

Question 17

Explain the doppler Effect

Answer 17

When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
If a car is moving, wavefronts of the sound are no longer evenly spaced.
Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.

Question 18

features of a transverse wave

Question 19

properties of EM waves

Answer 19

Transfer energy
Are transverse waves
Travel at the speed of light in a vacuum
Can be reflected and refracted

Question 20

features of a longitudinal wave

Answer 20

rarefactions and compressions
particles vibrate back and forth

Question 21

all EM waves travel at same speed in _____ ______

Answer 21

free space

Question 22

order of em waves from lowest to highest frequency

Answer 22

Radio Waves

Microwaves

Infrared (IR)

Visible Light

Ultraviolet (UV)

X – Rays

Gamma Rays

Question 23

which has the shortest wavelength and has the lowest frequency

Answer 23

radio waves

Question 24

which colour has the shortest wavelength and lowest frequency in the visible light spectrum

Answer 24

red

Question 25

Uses of EM waves: Radio Waves Microwaves Infrared (IR) Visible Light Ultraviolet (UV) X – Rays Gamma Rays

Answer 25

* radio waves: broadcasting and communications * microwaves: cooking and satellite transmissions * infrared: heaters and night vision equipment * visible light: optical fibres and photography * ultraviolet: fluorescent lamps * x-rays: observing the internal structure of objects and materials, including for medical applications * gamma rays: sterilising food and medical equipment.

Question 26

risks of exposure to EM waves: microwaves infrared ultraviolet gamma rays

Answer 26

* microwaves: internal heating of body tissue * infrared: skin burns * ultraviolet: damage to surface cells and blindness * gamma rays: leads to ionisation of cells causing mutation which might produce cancerous cells

Question 27

How to reduce risks of: UV gamma

Answer 27

UV = stay in shade, sunglasses, sun cream Gamma = led clothing, leave room - reduced exposure

Question 28

practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms

Answer 28

1. Set up your apparatus as shown in the diagram using a rectangular block. 2. Shine the light ray through the glass block 3. Use crosses to mark the path of the ray. 4. Join up crosses with a ruler 5. Draw on a normal where the ray enters the glass block 6. Measure the angle of incidence and the angle of refraction and add these to your results table 7. Comment on how the speed of the light has changed as the light moves between the mediums. 8. Repeat this for different angles of incidence and different glass prisms.

Question 29

refractive index = n =

Answer 29

sin (angle of incidence) / sin (angle of refraction) sin (i) / sin(r)

Question 30

practical: investigate the refractive index of glass, using a glass block

Answer 30

1. Set up your apparatus as shown in the diagram using a rectangular block. 2. Shine the light ray through the glass block 3. Use crosses to mark the path of the ray. 4. Join up crosses with a ruler 5. Draw on a normal where the ray enters the glass block 6. Measure the angle of incidence and the angle of refraction and add these to your results table 7. Calculate the refractive index 8. Repeat steps 2 – 7 using a different angle of incidence 9. Find an average of your results.

Question 31

practical: investigate the refractive index of glass, using a glass block

Answer 31

1. Set up your apparatus as shown in the diagram using a rectangular block. 2. Shine the light ray through the glass block 3. Use crosses to mark the path of the ray. 4. Join up crosses with a ruler 5. Draw on a normal where the ray enters the glass block 6. Measure the angle of incidence and the angle of refraction and add these to your results table 7. Calculate the refractive index 8. Repeat steps 2 – 7 using a different angle of incidence 9. Find an average of your results.

Question 32

describe the role of total internal reflection in transmitting information along optical fibres and in prisms

Answer 32

optical fibres - use light to carry digital information over long distances

Question 33

explain what is the critical angle and the 3 conditions

Answer 33

The angle of incidence which produces an angle of refraction of 90 (refracted ray is along the boundary of the surface). When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary). This effect only occurs at a boundary from a high refractive index material to a low refractive index material. When the angle of incidence is lesser than the critical angle, light partially internally reflected when the angle of incidence is equal to critical angle, lots of internal reflection and emerging ray along surface

Question 34

critical angle = c =

Answer 34

sin ^-1 (1/n)

Question 35

refractive index = n =

Answer 35

1 / sin(c)

Question 36

sound waves are longitudinal waves and light is transverse waves and both can be ______ and ______

Answer 36

reflected and refracted

Question 37

frequency range for human hearing

Answer 37

20–20 000 Hz

Question 38

explain journey of light ray from air into glass at angle and vice versa

Answer 38

Glass is denser than air, so a light ray passing from air into glass slows down. If the ray meets the boundary at an angle to the normal, it bends towards the normal. A light ray speeds up as it passes from glass into air, and bends away from the normal by the same angle.

Question 39

the denser the material, the ________ that light travels

Answer 39

slower (bends closer to normal)