CBSE Class 12 Physics Solved Question Paper 2015

Find CBSE Class 12 Physics Solved Question Paper 2015. These questions not only helps the students to prepare for exams in a better manner, but also helps them in understanding the depth with which a topic should be studied.

Few Sample Questions from the Question Paper are given below:

Q. What happens when a forward bias is applied to a p-n junction?

Sol. When p-n junction is forward biased, the holes are accelerated and they cross the barrier to reach in region of N type of semiconductor. This increases the current in the p-n junction circuit. The width of potential barrier deceases.

Q. Write the important characteristic features by which the interference can be distinguished from the observed diffraction pattern.

Sol. Difference Between Interference And Diffraction:

1) Interference is the superposition of waves originating from two coherent sources of light whereas diffraction is the superposition of the wavelets coming from different parts of wave fronts of a wave.

2) The interference pattern is of uniform brightness throughout , whereas in diffraction the brightness of fringes keeps decreasing with the rise in the diffraction pattern.

3) The fringe width of interference pattern may be equal or not, but in case of diffraction fringes are always of unequal width.

Q. Explain the basic differences between the construction and working of a telescope and a microscope.

Sol. Basic Difference In Between Microscope And Telescope:

(1) The compound microscope has convex lens of longer focal length as objective and eyepiece of shorter focal

(2) Tube Length Of Microscope, L= V_O + U_e, since  v₀ is constant whereas u_e can be varied. In case of telescope, length of the tube L= F_O+ U_e,

(3) A microscope is used for viewing a tiny object, whereas telescopes are used for watching distant and heavenly objects.

Q. Arrange the following electromagnetic wave in the order of their increasing wavelength:

(a) γ- rays

(b) Microwaves

(c) X-rays

(d) Radio waves

How are infrared waves produced? What role dose infra-red radiation play in (i) maintains the Earth’s warmth and (ii) physical therapy?

Sol. Following is the arrangement of electromagnetic wave in the increasing order of their wavelength:

a) Gamma rays

b) X-rays

c) Microwaves

d) Radio waves

(i) When sunlight falls on the atmosphere of earth, a major part of the ultraviolet radiation of sunlight is reflected in the space. The infrared radiations of sunlight are absorbed by the atmosphere after multiple reflection because infrared radiations are not energetic enough to go out of earth’s atmosphere. Infrared radiations has hot radiations so after multiple reflection, they heat up the atmosphere. Infrared radiations falling on earth and warm atmosphere keeps the surface of earth warm.

(ii) In physical therapy the warmth and heat energy of infrared radiations are used. These radiations provide a soothing effect in our muscles. They repair and heal up the weak cells and tissues.

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