question_answer1) What happens to the wavelength of photon after it collides with an electron?
View Answer play_arrowWhile watching TV a kid asked his mother about the broadcasting of TV programs. |
(i) What kind of is this kid? |
(ii) Which waves are used in a TV signals? |
Subhankar was making an electric bell. For that, he was looking for an appropriate material. Subham suggested him to use soft iron for this purpose and helped him in making electromagnet. |
(i) What quality do you think is there in Subham? |
(ii) Why Subham suggested for soft iron? |
In a single slit diffraction experiment, a slit of width d is illuminated by red light of wavelength 650 nm. For what value of d will |
(i) the first minimum fall is at an angle of diffraction of \[60{}^\circ \] and |
(ii) the first maximum fall is at an angle of diffraction of \[60{}^\circ ?\] |
During a thunderstorm, Ram and his friends were in the middle of a jungle. His friends were standing under a tree. Rohan advised them not to stand there. Rather he suggest they should move back to the bus. He explained them that they are safe inside the bus due to electrostatic shielding. |
(i) What are the values exhibited by Ram. |
(ii) What is electrostatic shielding? |
What do you understand by "sharpness of resonance" in a series L-C-R circuit? Write expression for Q-factor of the circuit. |
Or |
The magnetic flux passing perpendicular to the plane of a coil and directed into the paper is given by \[\phi =5{{t}^{2}}+6t+2,\] where \[\phi \] is in milliwebers and t in seconds. |
(i) What is the magnitude of the induced emf set up in the loop, t = 1 s? |
(ii) What is the direction of current through the resistor R? |
(i) Consider circuit in the figure. How much energy is absorbed by electrons from the initial state of no current (Ignore thermal motion) to the state of drift velocity? |
(ii) Electrons give up energy at the rate of \[R{{I}^{2}}\]per second to the thermal energy. Estimate the time scale associated with energy in problem (i) ? Given, n = number of electron per volume \[={{10}^{29}}\] per \[{{m}^{3}}.\] Length of circuit = 10 cm cross-section \[=A={{(1mm)}^{2}}.\] |
A doubly ionised lithium atom is hydrogen-like with atomic number Z = 3. Find the wavelength of the radiation required to excite the electron in \[L{{i}^{2+}}\] from the first to the thrid Bohr orbit. |
Given the ionisation energy of hydrogen atom as 13.6 eV. |
In Young's double slit experiment, the two slits 0.15 mm apart are illuminated by monochromatic light of wavelength 450 nm. |
The screen is 1.0 m away from the slits. |
(i) Find the distance of the second |
(a) bright fringe. |
(b) dark fringe from the central maxima. |
(ii) How will the fringe pattern change, if the screen is moved away from the slits? |
Double convex lens are to be manufactured from a glass of refractive index 1.5, with both faces of the same radius of curvature. What is the radius of curvature required, if the focal length is to be 30 cm? |
Or |
A Cassegrain telescope uses two mirrors as shown in figure below. Such a telescope is built with the mirrors 20 mm apart. If the radius of curvature of the large mirror is 220 mm and of the small mirror is 140 mm, then where will the final image of an object at infinity be? |
In the given figure, the wires AB, CD and EF have identical resistances. The separation between the neighbouring wire is 1.0 cm. |
The wires AE and BF have negligible resistance and the ammeter reads 15 A. |
Calculate the magnetic force per unit length of AB and CD. |
Geeta has dry hair. A comb ran through her dry hair attracts small bits of paper. She observes that Neeta with oily hair combs her hair, the comb could not attract small bits of paper. She consults her teacher for this and gets the answer. She then goes to the junior classes and shows this phenomenon as Physics experiment to them. |
All the juniors feel very happy and tell her that they will also look for such interesting things in nature and try to find the answers. She succeeds in forming a Science club in her school. |
Read the above passage and answer the following questions. |
(i) What according to you are the values displayed by Geeta? |
(ii) Explain the phenomenon involved. |
(iii) Why did the comb used by Neeta not attract the bits of paper? |
Amar got so much interested in astronomy that he decided to make a telescope. |
He studied about telescopes and its construction. He prepared his own astronomical telescope. He presented his observations in a science seminar and got first prize. |
(i) What qualities do you find in Amar? |
(ii) Draw ray diagram of astronomical telescope and give expression for its magnification. |
(i) The same input signal is applied to both the (input) terminals of a given logic gate. If the output is the |
(a) same as the (common) input signal. |
(b) inverted with respect to the (common) input signal. |
Identify the logic gates involved and write their truth tables in each case. Also draw output wave forms corresponding to inputs of each gate. |
(ii) Write the truth tables for each of the combinations shown below. Also, identify the logic operations performed by them. |
(i) Consider two coherent sources \[{{S}_{1}}\] and \[{{S}_{2}}\] producing monochromatic waves to produce interference pattern. Let the displacement of the wave produced by \[{{S}_{1}}\] be given by \[{{Y}_{1}}=a\cos \,\omega t\] and the displacement by \[{{S}_{2}}\] be \[{{Y}_{2}}=a\cos (\omega t+\phi )\] |
Find out an expression for the amplitude of the resultant displacement at a point and show that the intensity at that point will be \[I=4{{a}^{2}}{{\cos }^{2}}\frac{\phi }{2}\] Hence, establish the conditions for constructive and destructive interference. |
(ii) What is the effect on the interference fringes in Young's double slit experiment when (i) the width of the source slit is increased; (ii) the monochromatic source is replaced by a source of white light? |
OR |
Figure shows a modified Young's double slit experimental set up. where \[S{{S}_{2}}-S{{S}_{1}}=\frac{\lambda }{4},\] then |
(i) state the condition for constructive and destructive interference. |
(ii) define fringe width and obtain an expression for the fringe width |
(iii) locate the position of the central fringe. |
(i) Suppose, k is open and the rod moves with a speed v in the direction shown. Give the polarity and magnitude of the induced emf. |
(ii) What is the retarding force on the rod, when k is closed? |
(iii) How much power is required (by an external agent) to keep the rod moving at the same speed v when k is closed? |
(iv) How much power is dissipated as heat in the closed circuit? What is the source of the power? |
Or |
What are eddy currents? How are these produced? In what sense are eddy current undesirable in a transformer and how are these reduced in such a device? |
An induced emf has no direction of its own. Comment. |
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