paper 2 memorise Flashcards
(21 cards)
give examples of contact forces
friction, air resistance, tension and normal contact force.
give examples of non-contact forces
gravitational force, electrostatic force and magnetic force.
what do longitudinal waves show?
areas of compression and rarefaction.
what type of wave is a sound wave?
longitudinal
state EM spectrum
radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays
describe a method to measure speed of sound waves in air
- make a noise a known distance from a solid wall
- record the time for the echo to be heard
- use speed = distance/time
OR - have 2 mics connected to a datalogger at a large distance apart
- record the time difference between a sound passing one to other
- use speed = distance / time
describe a method to measure speed of ripples on a water surface
move a pencil along the paper at the same speed as a wavefront, and measure the time taken to draw this line. use speed = distance / time
how can sounds be heard?
outer ear collects the sound and channels down the ear canal. the sound waves hit the eardrum, the tightly stretches membrane which vibrates as the incoming pressure waves reach it. compressions forces eardrum forward. rarefaction forces backwards. eardrum vibrates at the same frequency as the sound wave. the stirrup bone also vibrates at same freq. these vibrations are passed to the fluid in the cochlea. small hairs that line the cochlea move too. each hair is sensitive to diff freq and is connected to a nerve cell which releases and electrical impulse to the brain.
why can humans only hear sounds between 20 Hz and 20k Hz?
in the cochlea, hairs that are tuned at higher frequencies can ide or get damaged. we evolved to hear this range as it gave us the best survival, we cannot hear ultrasound as we do not use sonar to hunt as we have accurate vision instead.
what can radio waves only be produced by?
by oscillations in electrical circuits.
how can radio waves create an alternating current?
When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit.
where do gamma waves come from?
changes in the nucleus of an atom.
how can EM waves be generated over a spectrum?
by changes in atoms and nuclei of atoms can result in electromagnetic waves being generated or absorbed over a wide frequency range
which 3 waves have hazardous effects on human body tissue
Ultraviolet waves, X-rays and gamma rays
what is the effect of UV rays on human tissue?
cause skin to age prematurely and increase the risk of skin cancer
what is the effect of xrays and gamma rays on human tissue?
ionising radiation that can cause the mutation of genes and cancer
where is infrared waves used?
electrical heaters, cooking food, infrared cameras
where is visible light used?
fibre optic communications
where is ultraviolet used?
energy efficient lamps, sun tanning
where is xrays and gamma rays used?
medical imaging and treatments.
