An object placed in front of a concave mirror of focal length 0.15 m produces a virtual image that is twice the size of the object. The position of the object with respect to the mirror is:

(1) -5.5 cm

(2) -6.5 cm

(3) -7.5 cm

(4) -8.5 cm

When a light ray from a rarer medium is refracted into a denser medium, its:

(1) Speed increases, wavelength increases

(2) Speed decreases, wavelength increases

(3) Speed increases, wavelength decreases

(4) Speed decreases, wavelength decreases

A narrow, paraxial beam of light is converging towards a point I on a screen. A plane plate of glass of thickness t and a refractive index $\mathrm{\mu }$ is introduced in the path of the beam. The convergence point is shifted by:

(1) t (1 - 1/$\mathrm{\mu }$) away

(2) t (1 + 1/$\mathrm{\mu }$) away

(3) t (1 - 1/$\mathrm{\mu }$) nearer

(4) t (1 + 1/$\mathrm{\mu }$) nearer

The length of a vertical pole at the surface of a lake of water $\left(\mu =\frac{4}{3}\right)$ is 24 cm. Then, to an under-water fish just below the water surface, the tip of the pole appears to be:

(1) 18 cm above the surface

(2) 24 cm above the surface

(3) 32 cm above the surface

(4) 36 cm above the surface

A microscope is focused on a coin lying at the bottom of a beaker. The microscope is now raised by 1 cm. To what depth should water be poured into the beaker so that the coin is again in focus?

(The refractive index of water is $\frac{4}{3}$)

(1) 1 cm

(2) 4/3 cm

(3) 3 cm

(4) 4 cm

Two transparent media A and B are separated by a plane boundary. The speed of light in medium A is 2.0 x 10⁸ ms^-1 and in medium B is 2.5 x 10⁸ ms^-1. The critical angle for which a ray of light going from A to B suffers total internal reflection is:

(1) sin^-11/2

(2) sin^-12/5

(3) sin^-14/5

(4) sin^-13/4

Which of the following is the possible application of fibre optics?

(1) Endoscopy

(2) High-speed internet traffic

(3) Radio, TV & Telephone signals

(4) All of these

The least distance between a point object and its real image formed by a convex lens of focal length F is:

(1) 2F

(2) 3F

(3) 4F

(4) Greater than 4F

The plane faces of two identical plano-convex lenses, each having a focal length of 40 cm, are placed against each other to form a usual convex lens. The distance from this lens at which an object must be placed to obtain a real, inverted image with a magnification of '-1' is:

(1) 80 cm

(2) 40 cm

(3) 20 cm

(4) 160 cm

Two thin lenses of focal lengths 20 cm and -20 cm are placed in contact with each other. The combination has a focal length equal to:

(1) Infinite

(2) 50 cm

(3) 60 cm

(4) 10 cm