Chapter 17 -Light and its phenomena

Above image shows REFRACTION, a phenomenon where light as a wave bends differently when entering a different medium. Refraction happens in a glass of water as well as in a glass prism.

A picture is worth a 1000 words. See a strong concentrated “Monochromatic Beam of Light” from a Laser hitting a plate having Two vertical Slits (rectangular holes) . The incoming Laser beam of Light undergoes Diffraction around the holes, comes out on the other side as Two different waves, these two waves undergo Interference , and this creates Bright and Dark bands (Fringes) on the screen.  It is another proof of the Wave Theory of Light.

Another different video , different topic altogether: I took this one day on a lovely beach, with the sun shining directly overhead. A boat was in the distance. The sea was glorious. Before you get jealous, I have to say I saw this phenomenon called SUN GLITTER . (Check wikipedia also) You will feel like you are seeing a thousand suns.

The physics behind it is that the water molecules on the waves (those which are angled towards our eyes), reflect the sun’s rays. (Angle of incidence = Angle of reflection) This simple formula becomes a beautiful natural phenomenon.

A physics explanation daigram :

This course explains about light , the one great thing in the big wide Universe that behaves both as a particle and as a Wave. Earlier it was thought by scientists that light must be a particle , they imagined trillions/zillions of light particles shooting out from the sun towards the earth. Later, it was proved by scientist Young in his famous “Young’s Double Slit experiment” that light has to be a WAVE.

Final verdict on the subject? Light behaves both as a wave and as a particle. Read on….

Following topics are covered:

1) Nature of Light – is it a wave or particle, or both?

2) More about light waves as Electromagnetic waves

3) Einstein’s Special Theory of Relativity, Speed of Light, Formula, Relative Velocity, Numericals

4) Coherent and Incoherent Waves of Light

5) Superposition of Waves and important things for Constructive versus Destructive Interference

6) Young’s Double-Hole experiment – a precursor to the Double Slit experiment

7) Young’s Double Slit experiment with perfectly Monochromatic and Coherent Light- 3D images, equations

8) Important Criteria to get clear fringes in Youngs Double Slit Experiment

9) Conceptual Difference between Interference and Diffraction

10) Interference due to Thin Films – pictures and sketches

11) Fresnel’s Biprism experiment – Refraction, Interference

• equation derivation

12) Coherent versus Incoherent waves

13) Diffraction of light

•     Fresnel Diffraction with Straight Edge
•     Fraunhofer Diffraction with Circular Hole.

14) THEORY TEST

15) NEET UG level Mock Test paper with Solutions