Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Physics

(a)

(b)

1. Name the type of a diode whose characteristics are shown in figure (A) and figure (B).
2. What does the point P in figure (A) represent?
3. What does the points P and Q in figure (B) represent?

A Zener of power rating 1 W is to be used as a voltage regulator. If zener has a breakdown of 5 V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of Rs for safe operation (Figure)?

If each diode in figure has a forward bias resistance of 25 Ω and infinite resistance in reverse bias, what will be the values of the current I₁, I₂, I₃ and I₄?

In the circuit shown in figure, when the input voltage of the base resistance is 10 V, V_be is zero and V_ce is also zero. Find the values of I_b, I_c and β.

Consider a box with three terminals on top of it as shown in figure (a):

(a)

Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement. A student performs an experiment in which any two of these three terminals are connected in the circuit shown in figure (b).

(b)

The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit. The graphs are

(i) when A is positive and B is negative

(c)

(ii) when A is negative and B is positive

(d)

(iii) When B is negative and C is positive

(iv) When B is positive and C is negative

(f)

(v) When A is positive and C is negative

(g)

(vi) When A is negative and C is positive

(h)

From these graphs of current-voltage characteristics shown in figure (c) to (h), determine the arrangement of components between A, B and C.

In a Young’s double slit experiment, the path difference at a certain point on the screen between two interfering waves is `1/8`th of the wavelength. The ratio of intensity at this point to that at the centre of a bright fringe is close to ______.

ASSERTION (A): In an interference pattern observed in Young's double slit experiment, if the separation (d) between coherent sources as well as the distance (D) of the screen from the coherent sources both are reduced to 1/3^rd, then new fringe width remains the same.

REASON (R): Fringe width is proportional to (d/D).

The graph of potential barrier versus width of depletion region for an unbiased diode is shown in graph A. In comparison to A, graphs B and C are obtained after biasing the diode in different ways. Identify the type of biasing in B and C and justify your answer

‘A’	‘B’	‘C’

Radiation of frequency 10¹⁵ Hz is incident on three photosensitive surfaces A, B and C. Following observations are recorded:

Surface A: no photoemission occurs

Surface B: photoemission occurs but the photoelectrons have zero kinetic energy.

Surface C: photo emission occurs and photoelectrons have some kinetic energy.
Using Einstein’s photo-electric equation, explain the three observations.

Draw V-I characteristics of a p-n Junction diode.

Differentiate between the threshold voltage and the breakdown voltage for a diode.

Write the property of a junction diode which makes it suitable for rectification of ac voltages.

A slit of width 0.6 mm is illuminated by a beam of light consisting of two wavelengths 600 nm and 480 nm. The diffraction pattern is observed on a screen 1.0 m from the slit. Find:

1. The distance of the second bright fringe from the central maximum pertaining to the light of 600 nm.
2. The least distance from the central maximum at which bright fringes due to both wavelengths coincide.

How will the interference pattern in Young's double-slit experiment be affected if the screen is moved away from the plane of the slits?

How will the interference pattern in Young's double-slit experiment be affected if the source slit is moved away from the plane of the slits?

How will the interference pattern in Young's double-slit experiment be affected if the phase difference between the light waves emanating from the two slits S₁ and S₂ changes from 0 to π and remains constant?

Explain the formation of the barrier potential in a p-n junction.

An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is

1. negative and
2. positive.

A point object is placed at O in front of a glass sphere as shown in figure.

Show the formation of the image by the sphere.

In Young's double slit experiment using light of wavelength 600 nm, the slit separation is 0.8 mm and the screen is kept 1.6 m from the plane of the slits. Calculate

1. the fringe width
2. the distance of (a) third minimum and (b) fifth maximum, from the central maximum.