A thin convex lens of refractive index 1.5 has 20 cm focal length in air. If the lens is completely immersed in a liquid of refractive index 1.6, its focal length will be

 

1.  -160 cm

 

2.  - 100 cm

 

3.  + 10 cm

 

4.  +100 cm

SI unit of permittivity is

 

A simple harmonic oscillator consists of a particle of mass m, and an ideal spring with spring constantk. The particle oscillates with a time period T. The spring is cut into two equal parts, Of one part oscillates with the same particles, the time period will

 

1.  2T

The coefficient of viscosity for hot air is

 

An artificial satellite moving in a circular orbit around the earth has a total (kinetic + potential) energyE₀. Its potential energy is

1.  -E₀

A thin hollow sphere of mass m is completely filled with a liquid of mass m. When the sphere rolls with a velocity v, kinetic energy of the system is (neglect friction)

 

1.  mv²

A non-conducting body floats in a liquid at 20 °C with of its volume immersed in the liquid. When liquid temperature is increased to 100 °C, of body’s volume is immersed in the liquid. Then the coefficient of real expansion of the liquid is (neglecting the expansion of container of the liquid)

 

1.  15.6×10^-4oC^-1

Two slabs A and B of different materials but of the same thickness are joined end to end to form a composite slab. The thermal conductivities of A and B are K₁ and K₂ respectively. A steady temperature difference of 12 °C is maintained across the composite slab. If K₁ = , the temperature difference across slabs A is

 

1.  4 °C

In short wave communication, waves of which of following frequencies will be reflected back by the ionospheric layer having electron density 10¹¹ per m³?

 

1.  2 MHz