An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears:

• 10 times taller.

• 10 times nearer.

• 20 times taller.

• 20 times taller.

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

• f/2

• 3f/4

• 2f

• 2f

In an experiment for determination of refractive index of glass of a prism by i− δ, plot, it was found that a ray incident at angle 35^o, suffers a deviation of 408 and that it emerges at angle 79^o ⋅ Ιn that case which of the following is closest to the maximum possible value of the refractive index?

• 1.5

• 1.6

• 1.7

• 1.7

Assuming human pupil to have a radius of 0.25 cm and a comfortable viewing distance of 25 cm, the minimum separation between two objects that human eye can resolve at 500 nm wavelength is:

• 1 μm

• 30 μm

• 100 μm

• 100 μm

On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens’ principle leads us to conclude that as it travels, the light beam:

• goes horizontally without any deflection

• bends downwards

• bends upwards

• bends upwards

Monochromatic light is incident on a glass prism of angle A. If the refractive index of the material oft the prism is μ, a ray incident at an angle θ, on the face AB would get transmitted through the face AC of the prism provided

7.

A thin convex lens made from crown glass  has focal length f. When it is measured in two different liquids having refractive indices 4/3 and 5/3, it has the focal lengths f₁ and f₂ respectively. The correct

•  f₁  = f₂ <f

•  f₁  >f and f₂ becomes negative

•  f₂  >f and f₁ becomes negative

•  f₂  >f and f₁ becomes negative

The diameter of the plano-convex lens is 6 cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2 × 10⁸ m/s, the focal length of the lens is 

• 15 cm

• 20 cm

• 30 cm

• 30 cm

A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with bigger loop is 

• 9.1 x 10^-11 Wb

• 6 x 10^-11 Wb

• 3.3 x 10^-11 Wb

• 3.3 x 10^-11 Wb

The graph between angle of deviation (δ) and angle of incidence (i) for a triangular prism is represented by