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You carried out an experiment to measure the wavelength of a monochromatic light source using a diffraction grating - Leaving Cert Physics - Question 2 - 2007
Question 2
You carried out an experiment to measure the wavelength of a monochromatic light source using a diffraction grating. The diffraction grating had 600 lines per mm. (... show full transcript
Worked Solution & Example Answer:You carried out an experiment to measure the wavelength of a monochromatic light source using a diffraction grating - Leaving Cert Physics - Question 2 - 2007
Step 1
Draw a labelled diagram of the apparatus you used.
Answer
In the diagram, include the following components:
- Diffraction grating (as per Young's slits).
- Monochromatic light source (e.g., sodium lamp).
- Spectrometer.
- Screen for observing diffraction patterns.
- A scale or measuring stick to measure distances.
Make sure the labels are clear and positioned appropriately.
Step 2
Step 3
State what measurements you took during the experiment.
Answer
The measurements taken during the experiment include:
- The distance from the diffraction grating to the screen (D).
- The distance between the first-order (n=1) and the second-order (n=2) diffraction fringes (x).
- Adjustments made using the spectrometer for accurate alignment.
Step 4
Step 5
How did you determine the wavelength of the light?
Answer
The wavelength () of the light can be determined using the diffraction formula: Where:
- is the wavelength.
- is the distance between the lines on the grating.
- is the angle of diffraction.
- is the order of the fringe observed. Rearranging this, the wavelength can be found as: .
Step 6
Give one precaution that you took to get an accurate result.
Answer
One precaution to ensure accurate results is to ensure proper calibration of the spectrometer. Additionally, eliminating external light can help reduce interference in the measurements, such as by conducting the experiment in a dark room.