4.1 Waves and vibrations

Question 1

what are waves that pass through a substance the same as

Answer 1

vibrations that pass through that substance

Question 2

how are sound waves that pass through the air created.

Answer 2

by making a surface vibrate so it sends compression waves through the surrounding air

Question 3

examples of waves that pass through a substance (mechanical waves)

Answer 3

sound waves
seismic waves
waves on string

Question 4

what happens when waves pass through a substance

Answer 4

the particles in the substance vibrate in a certain way which makes nearby particles vibrate in the same way and so on

Question 5

description of electromagnetic waves

Answer 5

oscillating electric and magnetic fields that progress through space without the need for a substance

Question 6

how em waves work

Answer 6

the vibrating electric field generates a vibrating magnetic field which vibrates a further electric field and so on

Question 7

which way is the direction of vibration of the particles of a longitudinal wave

Answer 7

parallel to the direction in which the wave travels

Question 8

examples of longitudinal waves

Answer 8

sound waves
seismic waves
P waves
slinky

Question 9

what is it called in a longitudinal wave when the waves are close together

Answer 9

compression

Question 10

what is it called in a longitudinal wave when the waves are far apart

Answer 10

rarefaction

Question 11

which way is the direction of wave vibrations in a transverse wave

Answer 11

perpendicular to the direction in which the wave travels

Question 12

examples of transverse waves

Answer 12

electromagnetic waves
S waves
waves on a wire/ string
waves on water

Question 13

when are transverse waves plane polarised

Answer 13

if the vibrations stay in one plane only

if the vibrations change from one plane to another the waves are unpolarised

Question 14

what cannot be done to longitudinal waves

Answer 14

they can’t be polarised

Question 15

how does unpolarised light from a lamp or a candle become polarised

Answer 15

if passed through a polaroid filter

the transmitted light is polarised as the filter only allows light through which vibrates in a certain direction according to the alignment of the filters molecules

Question 16

if unpolarised light is passed through 2 polaroid filters what is the transmitted light intensity charge according to

Answer 16

if one polaroid is turned relative to the other one

Question 17

when are the polaroid filters said to be crossed

Answer 17

when the light intensity emitted is a minimum

because the polarised light from the first filter can’t pass through the second filter as the alignment of of molecules in the second filter is 90 degrees to the alignment in the first filter

Question 18

what is the plane of polarisation of an electromagnetic wave defined as

Answer 18

the plane in which the electric field oscillates

Question 19

what do polaroid sunglasses do

Answer 19

reduce the glare of the light reflected by water or glass

the reflected light is polarised and the intensity is reduced when it passes through the sunglasses