• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Diffraction Grating with White Light Source

Extracts from this document...


Physics Laboratory Report

The number and the name of the experiment:

Experiment C3- Diffraction Grating with White Light Source
The date of experiment:19 / 5 / 08image00.jpg


  • Estimate the wavelength of the light using a diffraction grating
  • Measure the angle of diffraction by simple geometry
  • Measure the angle of diffraction by simple spectrometer
  • Learn the techniques in using a spectrometer



meter rule


set square(woodblock)




Diffraction grating(300 lines per mm)


ray box with vertical filament


12 V low voltage power supply


long pin




laboratory jack


color filter – red, green, blue

1 each

sodium lamp(optional)



In the visible wavelengths of the electromagnetic spectrum, red, with the longest wavelength, is diffracted most; and violet, with the shortest wavelength, is diffracted least. Because each color is diffracted a different amount, each color bends at a different angle. The result is a separation of white light into the seven major colors of the spectrum or rainbow. The diffraction grating consists of many narrow slits provided for the diffraction of the light.image02.jpg

Constructive interference occurs between waves from A traveling in the direction AA1 and waves from B traveling in the direction BB1.

...read more.


1  can be obtained using the formula tanΘ =

Finally, by substituting the values of Θ1and d

into the equation d sinθ1 = 1λ, the required

 wavelength can be calculated.


  1. Use the ray box with vertical filament. Place the lamp about 2 m away.
  1. Place two meter rules at right angles to each other as shown. Set the diffraction grating vertically at one end of the meter rule. Observe the horizontal diffraction pattern (color spectrum) of the filament by viewing through the diffraction grating.
  1. Ask the partner to move a long pin to the observer’s left hand side along the other meter rule until it lines up with the middle of the red band of the first order spectrum. Place the red filter in front of the lamp to helping locating the position.
  1. Repeat step 3 for the position on the observer’s right hand side with another pin. Find the separation, 2x, of the pins. Record the results in the table provided.
  1. Repeat step 3 and 4 for green and then blue.
  1. Determine the angles of diffraction for red, green and blue light.
...read more.



  • Whether it is better to use pins with the addition of laser bean rather than just pins to locate the position of the light to be found.

Explanation﹕Absolutely, it is better to accept this replacement. The principle of using the pins is to move the pins along the either side of the meter rule until it lines up with the middle of the red band of the first order spectrum in order in order to find out the exact position of the required light. As using the naked eyes to judge the middle point of the red region within its wide range is already really difficult, if we just use the mechanical work (moving the pins) to match up with the observer’s observation, tremendous error will exist due to the inexact human sensate system. Thus, by using the laser bean, we can first point out the relative middle position of the light, then moving the pins along the meter rule until it coincides with the infra-red light. It is no doubt that it will increases the accuracy of the results taken.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Waves & Cosmology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Waves & Cosmology essays

  1. Peer reviewed

    Black Holes Research and Report

    4 star(s)

    This occurrence would be enormously powerful and send gravitational waves through space-time. Gravitational waves are a fundamental prediction in Einstein's theory of general relativity, but have never been directly observed or detected in space. Gravitational Lensing A gravitational lens is an occurrence only caused by black holes and other immensely heavy objects.

  2. Peer reviewed

    What affects the voltage output of a solar panel?

    3 star(s)

    The reason for this could be that because the efficiency of the solar cell is only 23% and can only generate a maximum potential difference (of 1.44v, from results table), as it is saturated with photons from the light source.

  1. How power produced by a solar cell is affected by its distance from a ...

    To improve the accuracy I could increase the number of measurements at different distance I took. The anomalous results that I found when 1-2cm from the light also need further investigation with smaller cells that will give accurate results. The wires I used in my experiment were creating resistance and

  2. The aim of my coursework is to calculate the wavelength of red laser light ...

    the next one after is called 2nd order spectrum and so on. Calculation using the diffraction grating These below steps show the calculation when using the diffraction grating which then will be followed by the calculation when using the slits as they both have a slightly different method.

  1. Estimating the wavelength of light using a double-slit and a plane diffraction grating

    The path difference x between light diffracted from successive transparent lines is a multiple n of the wavelength ?: x= d sin? = n?, where n=0,1,2,3... is known as order number. If we can measure the angle of diffraction for the first order bright fringe, wavelength of the light source can be estimated using the formula ?= d sin?.

  2. Refractive index by tracing light rays

    % 2.17 % 1.85 % 1.47 % 1.39 % % error in sin i 2.06 % 1.52 % 1.23 % 1.07 % 0.964 % % error in sin r 2.99 % 2.23 % 1.92 % 1.56 % 1.48 % Percentage error in refractive index of glass (nglass)

  1. Investigate any relationship present between the distance between a solar cell and a lamp, ...

    Violet has the shortest wavelength of visible light, with around 400 x 10-9. So, with all electromagnetic waves travelling at 300 000 000 (3 x 108) m/s: 3 x 108 = 400 x 10-9 f (3 x 108) / (400 x 10-9)

  2. Waves and Cosmology - AQA GCE Physics Revision Notes

    The original radiation would have been in the visible region, but it has been red shifted as energy is lost from the photon due to expansion of the universe. * As a microwave receiver is set up, a signal of wavelength 735 cm was picked up when no signal was sent.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work