topic 3 - waves

Question 1

what is a longitudinal wave

Answer 1

A wave that oscillates at parallel to the direction in which energy is transferred e.g. sound

Question 2

what is a transverse wave

Answer 2

A wave that oscillates perpendicular to the direction in which energy is transferred
e.g. Light

Question 3

what is a wavefront

Answer 3

Created by overlapping lots of different waves. A wavefront is where all the vibrations are in phase and the same distance from the source.

Question 4

what is amplitude

Answer 4

The maximum displacement of particles from their equilibrium position.

Question 5

what is wavelength

Answer 5

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

Question 6

what is frequency

Answer 6

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

Question 7

what is time period

Answer 7

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

Question 8

what can waves transfer

Answer 8

Waves can transfer energy and information with out transferring matter, for example sun light, it transfers energy as it makes the earth warm without bringing any matter.

Question 9

relationship between speed, frequency and wavelength

Answer 9

speed - frequency x wavelength

v = f × λ

Question 10

how to calculate frequency

Answer 10

1/time period

1/T

Question 11

what is the Doppler Effect

Answer 11

• 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 12

4 properties of the electromagnetic spectrum

Answer 12

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

Question 13

order of electromagnetic spectrum

Answer 13

Radio Waves

Microwaves

Infrared (IR)

Visible Light

Ultraviolet (UV)

X – Rays

Gamma Rays

Question 14

uses of different levels of electromagnetic spectrum

Answer 14

• 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 15

detrimental effects of microwaves, infrared, UV and gamma rays

Answer 15

• microwaves: internal heating of body tissue
• infrared: skin burns
• ultraviolet: damage to surface cells and blindness
• gamma rays: cancer, mutation

Question 16

how to avoid detrimental effects

Answer 16

wear sun glasses, sun cream and stay in shade for UV
Wear led clothing for Gamma

Question 17

is light transverse or longitudinal

Answer 17

transverse

Question 18

what is the law of reflection

Answer 18

angle of incidence is equal to angle of reflection

Question 19

method for investigating refraction

Answer 19

• place a glass block on blank paper and trace it with a pencil
• shine the light ray through the glass block
• use crosses to mark the path of the ray.
• remove glass block
• join up crosses with a ruler
• draw on a normal where the ray enters the glass block
• measure the angle of incidence and the angle of refraction and add these to your results table
• repeat this for different angles of incidence and different glass prisms.

Question 20

how to calculate refractive index

Answer 20

sin i/sin r

Question 21

1 use of total internal reflection

Answer 21

Used to transmit signals along optical fibres.

Question 22

what is a critical angle

Answer 22

• 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 density to a low density

Question 23

how to find critical angle

Answer 23

sin^-1(1/n)

Question 24

can sound waves be reflected and refracted

Answer 24

yes and they are longitudinal