Waves, physics GCSE

flashcards for Edexcel GCSE = physics topic 4 (waves)

wavelength

distance between the same points on two consecutive waves

time period

time taken for one complete waves to pass a given point

amplitude

distance from equilibrium line to the maximum distance (crest or trough)

frequency

number of complete waves passing a given point per second

wavefront

the plane in which waves travel (direction of travel.)

wave speed

speed at which energy is transferred through medium.

longitudinal waves

oscillations are parallel to the direction of energy transfer. They consist of compressions and rarefations.

examples of longitudinal waves

sound waves, seismic P waves

transverse waves

oscillations are perpendicular to the direction of energy transfer

examples of transverse waves

light waves, seismic S waves, water waves, any EM waves

Measuring velocity - sound in air

1) make a noise at 50m from a solid wall

2) record time for the echo to be heard

3) then use speed = distance/time

4) have 2 microphones connected to a data logger at a large distance apart

5) record the time difference between sound passing from one to the other. Then use speed = distance/time.

Measuring velocity - ripples on water surface

1) Use a stroboscope which has the same frequency as the water waves

2) measure distance between the ‘fixed’ ripples and use velocity = frequency x wavelength

3) move a pencil along the paper at the same speed as a wavefront

4) erasure the time taken to draw this line and the length of the line

5) then use speed = distance/time

Effect of refraction of waves as material interfaces

1) waves pass from one medium to another

2) if passing into a more optically denser medium (from air to glass)

then: the wave will be refracted at the boundary and will change direction to bend towards the normal.

speed decreases. Wavelength decreases.

Energy of a wave is constant and energy is directly linked to frequency of wave. So if frequency is constant and speed decreases, wavelength must also decrease.

The light bends closer to the normal

The effect of reflection of waves as material interfaces

1) waves will reflect off a flat surface

2) the smoother the surfaces, the stronger the reflected wave is

3) rough surfaces scatter the light in all directions, so appear and not reflective.

4) the angle of incidence = angle of reflection

5) light will reflect if the object is opaque and is not absorbed by the material (the elections will absorb the light energy, then reemit it as a reflected wave

the effect of transmission of waves as material interfaces

1) waves will pass through a transparent material

2) the more transparent, the more light will pass through the material.

3) it can still refract, but the process of passing through the material and still emerging is transmission.

Effect of absorption of waves as material interfaces

1) if the frequency of light matches the energy levels of the electrons,

• the light will be absorbed by the electrons and not reemitted

• They will be absorbed and then reemitted over time as heat

• So that particular frequency has been absorbed

• if a material appears green, only green light has been reflected, and the rest of the frequencies in visible light have been absorbed.

Effects of wavelength

• different substances may absorb, transmit, refract or reflect depending on their wavelength

• Glass transmits/refracts visible light

• Reflects UV

what are the effects of a amplitude and the effect of wavelength

a wavelength Is something that has a

frequency

frequency of a wave is number of waves that pass a given point perfectly second