A concave mirror of focal length \(f\) produces an image \(n\) times the size of the object. If the image is real, then the distance of the object from the mirror is:
1. \((n-1)f\)
2. \(\frac{(n-1)}{n}f\)
3. \(\frac{(n+1)}{n}f\)
4. \((n+1)f\)

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