Green light ejects photoelectrons from a given photosensitive surface whereas yellow light does not. What will happen in case of |
(i) violet, and |
(ii) red light? |
Give reason for your answer. |
Obtain relations between |
(i) earth's magnetic field and its horizontal and vertical components, |
(ii) angle of dip and the horizontal and vertical components of the earth's magnetic field. |
The nucleus \[_{10}^{23}\] Ne decays by \[{{\beta }^{-}}-emission.\] Write down the \[\beta -decay\] equation and determine the maximum kinetic energy of the electrons emitted. Given that, \[m(_{10}^{23}Ne)=22.994466\,u,\] \[m(_{11}^{23}Na)=22.989770\,u.\] |
Or |
With the help of an example, explain, how the neutron to proton ratio changes during \[\alpha \text{-decay}\] of a nucleus. |
Mohan and his younger brother Sohan were at the restaurant. It was very clean there. None of the flies and insects were there. His younger brother asked him about the fluorescent UV lamp present at the corner. Mohan explained the functioning of UV lamp. How flies and insects get trapped by it? |
(i) What are the values shown by Mohan? |
(ii) Give the source of UV-rays. |
A ground receiver is receiving a signal at |
(i) 5 MHz and |
(ii) 100 MHz |
transmitted from a ground transmitter at a height of 300 m located at a distance 100 km. Identify whether it is coming via space wave or sky wave propagation or satellite transponder. Radius of the earth \[\simeq 6.4\times {{10}^{6}}m,\] \[{{N}_{\max }}\] of the ionosphere \[={{10}^{12}}\,\,{{m}^{-3}}.\] |
Rashmi's Grandfather was old. Due to some reasons, doctor suggested him to go through an endoscopic tests. Grandfather had never gone through any such test ever before. So, he was afraid. He thought that these tests will cause negative effects on his body organs. |
Therefore, he was not ready for endoscopy. Everyone tried to let him understand and convince him. But, he got ready only when his granddaughter Rashmi convinced him and explained that it is nothing but just a test in which light wave is involved and possessing total internal reflection, which is used to view and observe the internal parts of the body. |
(i) What are the values of grandfather and the granddaughter's relation displayed here? |
(ii) What is the basic principle used in optical fibre? |
A | B | Output |
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 0 |
(i) Identify the logic gate used and draw its logic symbol. |
(ii) If the output of this gate is fed as input to a NOT gate, name the new logic gate so formed. |
One night Vikas was preparing for his Physics exam. Suddenly, the light in his room went off and he could not continue his studies. His cousin brother Bablu who had come to visit him quickly responded and turn on the light of his mobile phone. After that, he fixed the blown out fuse and then he checked the wiring and located a short circuit. He rectified it and put a fuse wire. The light came to life again. Vikas had a sign of relief and continued his studies. |
(i) What are the values projected by Vikas and Bablu? |
(ii) Why did Bablu have to check the wiring? |
(iii) What is an electric fuse? What characteristics you would prefer for a fuse wire? |
(i) Deduce the expression for the emf induced in the conductor. |
(ii) Find the force required to move the rod in the magnetic field. |
(iii) Mark the direction of induced current in the conductor. |
(i) Explain with the help of diagram, how plane polarised light is obtained by scattering? |
(ii) Between two polaroids placed in crossesd position, a third polaroid is introduced. The axis of the third polaroid makes an angle of \[30{}^\circ \] with the axis of the crossed polaroid. Find intensity of transmitted light from the system assuming \[{{I}_{0}}\] be the intensity of polarised light obtained form the first polaroid. |
The oscillating electric field is |
\[{{E}_{y}}=30\sin \,[2\times {{10}^{11}}t+300\pi x]\,V{{m}^{-1}}\] |
(i) Obtain the value of the wavelength of the electromagnetic wave. |
(ii) Write down the expression for the oscillating magnetic field. |
In the famous conversation, Rakesh Sharma, the first. Indian astronaut in space, was asked by the Prime Minister Indira Gandhi as to how India looked from space. To which he replied, 'Sare jahan se accha' (better than the whole world). |
(i) Which scientific mode of communicating enabled the Prime Minister to speak to the astronaut? |
(ii) What type of modulation is required for commercial broadcast of voice signals? |
(iii) Which values are being reflected in the reply given by the astronaut? |
Two cells \[{{E}_{1}}\] and \[{{E}_{2}}\]connected as shown in figure have an emf 5 V and 9 V and internal resistance of \[0.3\,\Omega ,\] and \[1.2\,\Omega \] respectively. Calculate |
(i) the value of current flowing through If resistance of \[3\,\Omega .\] |
(ii) power dissipated in the resistance of \[6\,\Omega .\] |
The circuit in figure shows two cells connected in opposition to each other. Cell \[{{E}_{1}}\] is of emf 6V and internal resistance \[2\,\Omega \] the cell is of emf 4V and internal resistances \[8\,\Omega .\] Find |
(i) effective resistance of the circuit |
(ii) effective emf of the two cells and current in the circuit |
(iii) the potential difference between the points A and B. |
(i) A particle moving with velocity \[5\times {{10}^{6}}m/s\] has de-Broglie wavelength of 0.135 nm associated with it. Calculate its kinetic energy in eV. |
(ii) In which region of the electromagnetic spectrum, does this wavelength lie? |
Show that the shortest wavelength lines in Lyman, Balmer and Paschen series have their wavelengths in the ratio 1 : 4 : 9. |
Or |
Prove that the radius of the nth Bohr orbit of an atom is directly proportional to \[{{n}^{2}},\] where n is principal quantum number. |
A series L-C-R circuit with L = 0.12 H, C = 480 nF, \[R\text{ }=\text{ }23\,\Omega \] is connected to a 230 V variable frequency supply. |
(i) What is the source frequency for which current amplitude is maximum? Obtain this maximum value. |
(ii) What is the source frequency for which average power absorbed by the circuit is maximum? Obtain the value of maximum power. |
(iii) For which frequency of the source is the power transferred to the circuit half the power at resonant? |
What is the current amplitude at these frequencies? What is the 0-factor of the given circuit? |
Or |
(i) State Faraday's laws of electromagnetic induction. |
(ii) Figure below shows a rectangular conductor PQRS in which the conductor PQ is free to move in a uniform magnetic field B perpendicular to the plane of paper. |
The field extends from x = 0 to x = b and is zero for x > b, assume that only the arm PQ possesses resistance r. |
When arm PQ is pulled outward from x = 0 to x = 2b and is then moved backward to x = 0 with constant speed v, obtain the expressions for the flux and the induced emf. Sketch the variations of these quantities with distance \[0\le x\le 2b.\] |
Answer the following questions. |
(i) You have learnt that plane and convex mirrors produce virtual images of objects. Can they produce real images under such circumstances? Explain. |
(ii) A virtual image, we always say, cannot be caught on a screen. |
Yet when we see a virtual image, we are obviously bringing it on to the 'screen' (i.e. the retina) of our eye. Is there a contradiction? |
(iii) A diver under water, looks obliquely at a fisherman standing on the bank of a lake. Would the fisherman look taller or shorter to the diver than what he actually is? |
(iv) Does the apparent depth of a tank of water change if viewed obliquely? If so, does the apparent depth increase or decrease? |
(v) The refractive index of diamond is much greater than that of ordinary glass. Is this fact of some use to a diamond cutter? |
Or |
(i) State Huygens' principle. Using this principle, draw a diagram to show how a plane wavefront incident at the interference of the two media gets refracted when it propagates from a rarer to a denser medium. Hence, verify Snell's law of refraction. |
(ii) Is the frequency of reflected and refracted light same as the frequency of incident light? |
Given figure shows a charge array known as an electric quadruple. For a point on the axis of the quadruple, obtain the dependence of potential on r for \[r/a>>1\] and contrast your results with that due to an electric dipole and an electric monopole (i.e. a single charge). |
Electric quadruple |
OR |
(i) Describe schematically the equipotential surfaces corresponding to |
(a) a constant electric field in the Z-direction, |
(b) a field that uniformly increases in magnitude but remains in a constant (say Z) direction and |
(c) a single positive charge at the origin. |
(ii) What is the effect on the interference fringes to a Young's double slit experiment when |
(a) the separation between the two slits is increased? |
(b) the width of the source-slit is decreased? |
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