Institute:Uie Department: Academic Unit 1&4
Institute:Uie Department: Academic Unit 1&4
Institute:Uie Department: Academic Unit 1&4
5
Apparatus Required
S.No. Equipment Range Quantities in
No.
Power Supply/
1 Operating Voltage 5mV/3-12V 1
2 1
Laser 400-700 nm
1
3 Diffraction Grating 200-500lines per
mm
4 Screen NA 1
6
Laser
7
Working of Laser
Lasers work to amplify a light source and
turn it into one powerful, concentrated
beam.
8
Diffraction Grating
9
Screen
• Light rays that pass through such a
surface are bent as a result of
diffraction, related to wave properties
of light.
10
Theory
11
Theory
d sin θ =n λ
d =n λ /sin θ (1)
13
Diffraction pattern diagram
14
Procedure
• Fix the graph paper on the screen and place it at appreciable distance D from
grating so that distinct maxima are seen.
• Mark the central brightest spot and maxima on both side of central maximum.
• Using a scale find the distance between first maxima on either side of central
spot.
15
Procedure
Repeat the steps 4 and 5 for 2nd and 3rd maxima. Then use these values to
calculate grating element d from equation (1).
16
Observation table & Calculations:-
Wavelength of Diode laser, λ=650 nm
Position of nth
order maxima Mean
Distance
distance of
between
nthorder
Order of Grating d=nλ/Sinθ
S.No. On left On right maxima (m)
diffraction (n) and screen
(OPn) (OPn′) from zeroth
(D)
m Cm order OP n
(m)
(m)
1.
2.
3.
Mean value of grating element, d=______________________m 17
Result
18
Sources of error
The main sources of error are the distance between the laser and the wall,
and the size of the dots. There is a further enlargement of the dots due to
attenuation as it passes through the air. This experiment would have been
more accurate if executed in a vacuum.
The dots on the extreme edges are also larger than they needed to be since
the light is spread out and it is hitting the surface (the wall) at an angle.
19
Learning Outcomes
• On completion students will be able to understand
• Diffracted lights shine on a distant screen which has a central bright spot
labelled m=0 and a higher order bright fringes that can also be observed.
20
Summary
• Working of Laser
• Description of Equipments.
• Observation table.
• Result
21
Viva Voice Questions
What is diffraction?
Define Grating?
How many orders of spectra possible for grating of 15000 lines per inch?
• Simulation Link:-
https://ophysics.com/l5b.html
1. https://www.youtube.com/watch?v=CxS8cfqg1a0
2. https://www.youtube.com/watch?v=71Rp-jG6Eek
23
References
1. https://images.app.goo.gl/onXTfVDfo1WiwTcK9
2. https://in.pinterest.com/pin/842243567793191631/
3. https://in.pinterest.com/pin/842243567793191631/
4. https://sustainablenano.files.wordpress.com/2013/02/laser2.png
5. http://physicsnet.co.uk/wp-content/uploads/2010/08/diffraction-grating-pic.jp
g
6. https://holmarc.com/differ_screen.php
7. https://vlab.amrita.edu/userfiles/1/image/laser/wave.JPG
8. https://physicsopenlab.org/wp-content/uploads/2016/03/slitDiffraction.gif
9. https://openstax.org/books/university-physics-volume-3/pages/4-4-diffraction-
grating
s
24
THANK YOU
For queries:deepak.e1972@cumail.in