ch6 practicals Flashcards
what is an oscilloscope
what do x and y represent
how to use to measure frquency
an oscilloscope shows how the potential difference across a component varies with time
the y-values shows pd, x shows time, you can change these values
connecting a signal generator produces a trace, find time period by measuring distance of one wavelenth and noting the timebase, do 1/ t to get frequency
how to find refractive index for transparent block
set up as shown.
measure angle of refraction for range of angles of incidence
calculate sin i and sin r for each pair
plot on graph sin i (y) against sin r (x),gradient is refractive index
uncertainties in i and r angles will produce uncertainties in sin i and sin r, so there will be an uncertainty in the gradient and so uncertainty in the refractive index
set up to view standing waves on a rubber cord
how to get velocity of progressive waves
set up apparatus as shown, making sure to stretch cord to twice its length.
use vibration generator to increase frequency until you eventually see the first standing pattern which will be the fundamental frequency, 2 nodes and an antinode in the middle
when this frquency is doubled you see the second harmonic, increasing further will give you more standing patterns
to get velocity, measure wavelength of standing wave, get frequency from generator, v = f * lambda
how to find speed of sound in air using resonance tube
you can find the speed of sound in air using a resonance tube with one end in water. you need a tuning fork of known frequency
hold a tuning fork above the tube to find L1, the shortest length of tube that increases the amplitude of the sound from the tuning fork. here there will be a node at the surface and an antinode just above the tube. L1 + k (a correction) will be equal to a quarter wavelength
when there’s 3 times as much of the tube out the water, L2, the amplitude will increase. here L2 + k will give 3/4 of the wavelength
L2 - L1 = 0.5 wavelength
v = f * lambda
how to determine wavelength of light using double slit
uncertainties
to determine wavelength of light using interference you need:
slit separation d, dist from slit to screen L should be few metres, fringe separation x
greatest ucnertainty is measuring slit seperation. if using diffraction grating, use number of lines per mm, * by 1000, divide by 1 to get a precise slit seperation answer
tan theta = x/L sin theta = lambda / d
small angle approximation sin theta = tan theta
x/L = lambda / d
wavelength = xd / L
