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### Course: Physics library>Unit 14

Lesson 2: Interference of electromagnetic waves

# Young's double slit introduction

We can see interference in action if we shine laser light through two slits onto a screen. Explore Young's Double Slit experiment, a cornerstone in understanding light as a wave. Discover how light waves spread out, overlap, and create patterns of constructive and destructive interference. Uncover the rules of wave interference in two dimensions, and how path length differences lead to these intriguing patterns. Created by David SantoPietro.

## Want to join the conversation?

• Does this mean that if we put a speaker behind a slit and we stand on the other side, we will hear the sound louder at one point and softer at the other?
• In a sense, yeah, if you're standing at a point where both the waves interact in such a way that they aren't in phase, in that case, they'll cause destructive interference
(1 vote)
• Aren't the bright fringes supposed to be of same intensity in Young's double slit experiment ?
• No As the Light wave travels further the intensity (of the light wave) starts dropping, thus causing a drop in intensity as you travel farther from the middle spot.
• why does the amplitude go on decreasing from the centre?
• Because, as you can see in the interference pattern, the number of interfering waves decreases, which means lesser and lesser constructive interference and thus the intensity goes on decreasing.
• at you say that the distance has to be comparable, why? I have learnt that if the distance is smaller than lambda then we wouldn't be able to see the pattern, why?
• Can someone explain to me what would happen if it were the same experiment but with a monochromatic or dichromatic light? Thanks in advance
(1 vote)
• laser beams give monochromatic light. well their waves can be specified to 1nm. central fringe will be double the width of the other fringes. all fringes will be same colour (colour of the light). the further the fringe is from the centre the less intense/bright it will be. I have no idea about dichromatic
• At , the wave diffracts to form circular waves. How do you identify the peaks and the valleys in the circular waves?
(1 vote)
• Circular boundaries define the peaks of the light wave. While at the exact middle distance between two circular boundaries you will find the valleys/ troughs.
(1 vote)
• What is the relationship between phase difference and path difference?
(1 vote)
• The phase difference is the difference in the phase angle of the two waves. Path difference is the difference in the path traversed by the two waves. The relation between phase difference and path difference is direct. They are directly proportional to each other.
(1 vote)
• in constructive interference, when the trough superimposes another trough, we get a dark spot. and in destructive interference when the crest superimposes a trough, we get a dark spot.so if only constructive interference happens, would we get bright and dark spots?
• yeahh.. sort of...but this time bright will be more bright..