Unit 6 - Waves Flashcards
What do waves do?
Transfer energy without transferring matter
What is a longitudinal wave?
A wave where the movement of particles is parallel to the direction of the wave, such as sound and p waves
What is a transverse wave?
A wave where the movement of particles is perpendicular to the direction of the wave, such as water, s waves
How do we hear sound?
Sound waves cause your eardrum to vibrate, sending signals to the brain. Human hearing range is 20Hz to 20 kHz
What is ultrasound?
A sound with a frequency of over 20kHz
What happens when sound meets a boundary?
Between two mediums, some sound is transmitted (passes through) while some is reflected. The resulting echoes can be timed to build up images of what’s out of view, such as a baby in a womb or fish under a boat (sonar)
How do we know the Earth has a molten core?
Longitudinal p waves can travel through liquids but s waves cannot, meaning due to the fact there is no aftershock on the other side of the world there must be a molten (liquid) core
What is specular reflection?
Reflection off a smooth surface. The angle of reflection is equal to the angle of incidence relative to the normal
What is diffuse reflection?
Reflection off a rough surface
How are EM waves produced?
When electrons lose energy, losing energy as an EM wave. Higher frequencies mean more energy carried by the wave. Gamma rays are emitted by nuclei, meaning more energy is involved which is why they are so dangerous
What happens when the energy of the wave is high enough?
The electrons can leave its atom, leaving ions. UV, X-rays and gamma are ionising radiation
What is refraction?
When waves enter a new medium and change speed as well as their angle
What happens when the wave slows down?
It bends towards the normal, meaning the angle of refraction is smaller than the angle of incidence. If speed decreases, wavelength also decreases while frequency stays constant
Why does light disperse through a prism?
Different wavelengths are refracted different amounts. When light exits, it speeds up again and bends away from the normal
What do concave lenses do?
Always diverge light rays, producing a virtual image that is diminished and upright
What is a black body?
A theoretical object that perfectly absorbs and emits all wavelengths of radiation
What happens if rate of absorption is greater than rate of emission?
Temperature increases, in turn increasing rate of emission
