**Aim**: To determine the wavelength of Laser using one dimensional diffraction grating.

**Apparatus used in the experiment**: Laser, one dimensional diffraction grating, ruler, screen.

**Apparatus to be used by you**: 15cm or 30cm ruler.

**Figure**:

**Formula**:

where,

*d* = grating element,

*n* = order of maxima,

*θ* = angle between central maxima and first order maxima ,

*λ* = wavelength of laser

**Procedure**:

- Setup for the experiment is as given below.

- Laser is focused on the screen and grating is placed between the laser source and screen.

- The photographs of diffraction pattern for different distances between the screen and the grating are given below.
- The distance between the grating and the screen,
*D*is mentioned on each photograph, which can be seen by magnifying the photograph.

- Generate the data with 1% uncertainty in the measurement, from the photographs above.
- Plot a suitable graph and determine the wavelength of laser only from the slope of the graph.
- The grating used in the experiment has 12868 lines/inches.

Click below to download high resolution images (if needed):

- Diffraction pattern for D = 17.0 cm
- Diffraction pattern for D = 16.0 cm
- Diffraction pattern for D = 15.0 cm
- Diffraction pattern for D = 14.0 cm
- Diffraction pattern for D = 13.0 cm
- Diffraction pattern for D = 12.0 cm
- Diffraction pattern for D = 11.0 cm
- Diffraction pattern for D = 10.0 cm

**Observations**:

In order to get your response, we are providing you with a google form. So that, we can get an idea about

- your data collection techniques,
- variables chosen for measurements,
- your data and
- the graphs that you will plot.

The google form: https://docs.google.com/forms/d/1LkTVewvaICMcGZBV__vBta59x6j2IIC5sFdiNBCzZCM/edi

Use the spreadsheet for calculations if needed: spreadsheet

You may download the graph sheet to plot the graph: Graph Sheet

**Note: **

What is meant by 1% uncertainty in the measurement of data?

When we say that we want to measure a variable, *y* with 1% uncertainty, it means that

It means that the measured quantity is at least 100 times the least count.

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