Physics Paper 2

Waves

Transfer energy without transferring matter

Longitudinal wave

• Vibrations are parallel to the direction of the wave

• Consist of compression & rarefractions

Transverse wave

Vibrations are at right angles (perpendicular) to the direction of the wave

Frequency =

1 / time period

What is A

Amplitude

What is B

Wave length

What is C

Peak/crest

What is D

Trough

What is E

Energy transfer

How does a human hear?

Sound waves cause your eardrum to vibrate, which sends a signal to your brain.

Human hearing range

• 20Hz to 20kHz

• frequency above 20kHz is called ultrasound

How does sonar work?

• When sound meets a boundary between two mediums (materials), some sound is TRANSMITTED (passes through), while some is REFLECTED

• The resulting echoes can be timed to build up a image of what's out of view e.g. a baby in a womb, or ocean floor underneath a boat.

How do we know the earth has a molten (liquid) core?

The fact that seismic P-waves (longitudinal) pass through the centre of the Earth while S-waves (transverse) do not

P wave

are faster, longitudinal waves that can travel through solids and liquids

S wave

are slower, transverse waves that can only travel through solids

Specular reflection

• Smooth surfaces (mirror) reflect light in a single clear direction.

• Angle of incidence = angle of reflection, both measured from the normal.

Diffuse reflection

Rough surfaces scatter light in many directions because the surface is uneven.

No clear reflected image.

EM(electromagnetic) waves

• Special since they dont need a medium to travel through

• Only wave that can travel through a vacuum in space

• Produced when an electron loses energy(gamma is emitted by nuclei)

• Can be absorbed by an electron

EM wave spectrum (Lowest to highest frequency)

• Radio waves

• Micro waves

• Infrared

• Visible light

• Ultra violet

• X-rays

• Gamma rays

Refraction

• When waves enter a new medium (material), their speed changes, as does their angle

• If speed decreases wavelength also does, while frequency stays constant

• If wave slows down it bends towards the normal

• When light exits it speeds up again and bends away from the normal