Required Practicals
- Created by: kennedylily
- Created on: 14-04-18 10:47
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1. An investigation into the variation of the frequency of stationary waves on a string with length, tension and mass per unit length of the string
- Set up the apparatus as shown with a 1.000m string length
- Increase frequency of signal generator from 0 until string vibrates at its fundamental frequency (ie. first harmonic)
- Record this frequency
- Repeat with string lengths of 0.900, 0.800, 0.700, 0.600 and 0.500m
- Repeat experiment again and find the mean value of f for each value of l
- plot graph of mean 1/f against l
- Draw the line of best fit and find gradient; graph should be a straight line through the origin
- The speed of travelling waves on string = fλ. When the string is vibrating at its fundamental mode, λ = 2l, hence λ = 2fl. The gradient is 1/fl so is given by 2/gradient in ms^-1
2. Investigation of the interference effects by Young's slit and diffraction by a diffraction grating
Young's slit experiment:
- Set up the apparatus as shown in the diagram, with the laser illuminating the double slit (or use a single slit if the laser beam isn't wide enough to illuminate the double slit), and the screen a distance D of about 1 metre
- The fringe width, w, of the interference pattern can be measured by measuring across a large number of visible fringes
- Use a metre ruler to measure D
- Find the slit separation, s, by reading what the manufacturer has quoted on the slide
- Plot a graph of w against D; this should be a straight line through the origin. The gradient represents λ/s
Interference by a diffraction grating:
- Set up the apparatus as shown in the diagram, with the laser illuminating the diffraction grating, and the screen a distance D of about 1 metre
- Adjust the position of the diffraction grating so that it is perpendicular to the beam of light from the laser
- The diffraction pattern should be visible on the screen
- The value of θ can be determined by measuring the distances y and D; the angle can then be calculated using tan^-1(y/D)
- The formula nλ = dsinθ can be used to calculate the wavelength of light; n is the order of the diffraction pattern, d is the grating spacing = 1/ no. of lines per metre, and λ is the wavelength of light
- The values of θ for each order, both above and below the zero order, should be measured
- A mean value for λ can be calculated from the data
3. Determination of g by a free-fall method
- Set up the apparatus as shown in the diagram
- The height between the starting position of the ball bearing and the upper light gate should be kept constant so that the velocity, u, is also constant
- Adjust the position of the lower light gate so that h is 0.500m
- Switch on the supply to the electromagnet and hang the ball bearing from it
- Reset the clock…
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