A beam of unpolarized light of intensity I₀ is passed through a Polaroid A and then through another polaroid B which is oriented so that its principal plane makes an angle of 45° relative to that of A.The intensity of the emergent light is

• I₀

• I₀/2

• I₀/4

• I₀/8

A cylindrical tube, open at both ends, has a fundamental frequency, f, in the air. The tube is dipped vertically in water so that half of it is in water. The fundamental frequency of the air-column is now

• f

• f/2

• 3f/4

• 2f

A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of this circle in cm is

• 
• 
• 
• 

B.

A green light is an incident from the water to the air – water interface at the critical angle (θ). Select the correct statement

• The entire spectrum of visible light will come out of the water at various angles to the normal.

• The spectrum of visible light whose frequency is less than that of green light will come out to the air medium

• The spectrum of visible light whose frequency is more than that of green light will come out to the air medium.

• The entire spectrum of visible light will come out of the water at an angle of 900 to the normal.

A mixture of light, consisting of wavelength 590 nm and an unknown wavelength, illuminates Young's double slit and gives rise to two overlapping interference patterns on the screen. The central maximum of both lights coincide. Further, it is observed that the third bright fringe of known light coincides with the 4th bright fringe of the unknown light. From this data, the wavelength of the unknown light is

• 393.4 nm

• 885.0 nm

• 442.5 nm

• 776.8 nm

C.

442.5 nm