51.

A transparent cube of 0.21 m edge contains a small air bubble. Its apparent distance when viewed through one face of the cube is 0.10 m and when viewed from the opposite face is 0.04m. The actual distance of the bubble from the second face of the cube is

• 0.06 m

• 0.17 m

• 0.05 m

• 0.04 m

White light is incident on one of the refracting surfaces ofa prism ofangle 5°. Ifthe refractive indices for red and blue colours are 1.641 and 1.659 respectively, the angular separation between these two colours when they emerge out of the prism is

• 0.9°

• 0.09°

• 1.8°

• 1.2°

For a given lens, the magnification was found to be twice as large as when the object was 0.15 m distant from it as when the distance was 0.2 m. The focal length of the lens is 

• 1.5 m

• 0.20 m

• 0.10 m

• 0.05 m

To a fish under water, viewing obliquely a fisherman standing on the bank of a lake, the man looks

• taller than what he actually is

• shorter that what he actually is

• the same height as he actually is

• depends on the obliquity

A thin prism P₁ with angle 4° made from a glass of refractive index 1.54 is combined with another thin prism P₂ made from glass of refractive index 1.72 to produce dispersion without deviation.The angle of the prism P₂ is

• 5.33°

• 4°

• 3°

• 2.6°

Specific rotation of sugare solution is 0.5 deg m²/kg. 200 kgm^-3 of impure sugar solution is taken in a sample polarimeter tube of length 20 cm and optical rotation is found to be 19°. The percentage of purity of sugar is

• 20 %

• 80 %

• 95 %

• 89 %

To a germanium crystal equal number of aluminium and indium atoms are added. Then

• it remains an intrinsic semiconductor

• it becomes a n-type semiconductor

• it becomes a p-type semiconductor

• it becomes an insulator

Maxium velocity of the photoelectrons emitted by a metal surface is 1.2 x 10⁶ ms^-1. Assuming the specific charge of the electron to be 1.8 x 10¹¹ C kg^-1, the value of the stopping potential in volt will be

• 2

• 3

• 4

• 6

Which of the following figures represents the variation of particle momentum and associated de-Broglie wavelength ?

If r₁ and r₂ are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r₁/r₂) is

• $\frac{64}{125}$

• $\sqrt{\frac{64}{125}}$

• $\frac{5}{4}$

• $\frac{4}{5}$