51.

The magnetic flux linked with the coil varies with time as . The magnitude of the induced emf at 2 s is

• 9 V

• 16 V

• 3 V

• 4 V

A 5O mH coil carries a current of 2 A, the energy stored in joule is

• 1

• 0.05

• 0.1

• 0.5

Velocity of electromagnetic waves in a medium depends upon

• thermal properties of medium

• mechanical and electrical properties of medium

• electrical and magnetic properties of the medium

• mechanical and magnetic properties of the medium

An electron enters uniform electric field maintained by parallel plates and of value E Vm^-1 with a velocity v ms^-1, the plates are separated by a distance d metre, then acceleration of the electron in the field is

• $\frac{\mathrm{Ee}}{\mathrm{m}}$

• $\frac{-\mathrm{Ee}}{\mathrm{m}}$

• $\frac{\mathrm{Ed}}{\mathrm{md}}$

• $\mathrm{Ee} \frac{\mathrm{d}}{\mathrm{m}}$

Band spectrum is also called

• molecular spectrum

• atomic spectrum

• flash spectrum

• line absorption spectrum

A fish at a depth of 12 cm in water is viewed by an observer on the bank of a lake. To what height the image of the fish is raised ? (Refractive index of lake water = 4/3). 

• 9 cm

• 12 cm

• 3.8 cm

• 3 cm

A ray of light is incident at 50° on the middle of one of the two mirrors arranged at an angle of 60° between them. The ray then touches the second mirror, gets reflected back to the first mirror, making an angle of incidence

• 50°

• 60°

• 70°

• 80°

A lamp (point source) is hanging along the axis of a circular table of radius r. At what height should the lamp be placed above the table so that the illuminance at the edge of the able is $\frac{1}{8}$ of that at its centre ?

• $\frac{\mathrm{r}}{2}$

• $\frac{\mathrm{r}}{\sqrt{2}}$

• $\frac{\mathrm{r}}{\sqrt{3}}$

• $\frac{\mathrm{r}}{\sqrt{7}}$

The focal length (f) of a spherical (concave or convex) mirror of radius of curvature R is

• $\frac{\mathrm{R}}{2}$

• R

• $\left(\frac{3}{2}\right)\mathrm{R}$

• 2R

In a compound microscope, the intermediate image is

• virtual, erect and magnified

• real, erect and magnified

• real, inverted and magnified

• virtual, erect and reduced