4.3- WAVE PROPERTIES 1

Question 1

Examples of wave properties? (3)

Answer 1

reflection
refraction
diffraction

Question 2

What can be used to study wave properties?

Answer 2

ripple tank

Question 3

What is a ripple tank?

Answer 3

shallow transparent tray of water with slopping sides

Question 4

What do the slopes of a ripple tank do?

Answer 4

prevent waves reflecting off sides of tank

Question 5

What would happen if the waves did reflect in a ripple tank?

Answer 5

would be difficult to see waves

Question 6

What are waves observed in a ripple tank called?

Answer 6

wavefronts

Question 7

What are wavefronts?

Answer 7

lines of constant phase (e.g. crests)

Question 8

What is the direction in which a wave travels like in comparison to the wavefront?

Answer 8

direction in which a wave travels is at right angles to wavefront

Question 9

What do waves directed at a certain angle to a hard flat surface (reflector) do? (hint- reflect)

Answer 9

reflect off at same angle

angle between reflected wavefront + surface is same as angle between incident wavefront + surface

Question 10

What can be said about the direction of the reflected wave as the angle between the reflected wavefront + surface is the same as the angle between the incident wavefront + surface? (reflection)

Answer 10

direction of reflected wave at same angle to reflector as direction of incident wave

Question 11

When is the effect of reflection observed?

Answer 11

when light ray directed at plane mirror

Question 12

What is the angle between the incident ray and the mirror like when a light ray is directed at a plane mirror? (reflection)

Answer 12

equal to angle between reflected ray + mirror

Question 13

What changes when waves pass across a boundary? (2)

Answer 13

wave speed changes

wavelength changes

Question 14

What happens if a wavefront approaches a boundary at an angle? (reflection)

Answer 14

change direction as well as changing speed- refraction

Question 15

Why does refraction happen when water waves in a ripple tank pass across a boundary from deep to shallow water at an angle to the boundary?

Answer 15

they move more slowly in shallow water, wavelength is smaller in shallow water so change direction

Question 16

When is refraction of light observed?

Answer 16

when light ray directed into glass block at an angle

Question 17

What happens when light ray is directed into a glass block at an angle?

Answer 17

light ray changes direction when it crosses glass boundary

Question 18

Why does the light ray change direction when it crosses the glass boundary? (refraction)

Answer 18

light waves travel more slowly in glass than in air

Question 19

When does diffraction occur?

Answer 19

when waves spread out after passing through a gap or round an obstacle

Question 20

When can the effect of diffraction be seen?

Answer 20

in ripple tank when straight waves directed at gap

Question 21

What happens when diffraction is being observed in a ripple tank (straight waves directed at gap) and the gap is now narrower?

Answer 21

narrower the gap, the more the waves spreads out

Question 22

What happens when diffraction is being observed in a ripple tank (straight waves directed at a gap) and the wavelength is now longer?

Answer 22

longer the wavelength, the more the waves spread out

Question 23

To consider why waves are diffracted on passing through the gap, what should each point on a wavefront be considered as?

Answer 23

as a secondary emitter of wavelets

Question 24

How do the wavelets from the points along a wavefront travel? (diffraction)

Answer 24

only in direction in which wave travelling, not in reverse direction, + combine to form new wavefront spreading beyond gap

Question 25

Where do satellite TV dishes in Europe need to point?

Answer 25

south

Question 26

Why do satellite TV dishes in Europe need to point south?

Answer 26

as satellites orbit Earth directly above the equator

Question 27

What happens the bigger the satellite TV dish?

Answer 27

the stronger the signal it can receive

Question 28

Why can bigger satellite TV dishes receive stronger signals?

Answer 28

as more radio waves are reflected by the dish onto the aerial

Question 29

What is a disadvantage of a bigger satellite TV dish?

Answer 29

reflects radio waves to smaller focus, as it diffracts waves less

Question 30

What happens as bigger satellite TV dishes reflect radio waves to a smaller focus?

Answer 30

dish needs to be aligned more carefully than smaller dish, otherwise it will not focus radio waves on aerial