Explanation:
For a linearly polarised, plane electromagnetic wave,
$\text{E}=\text{E}_0\sin\omega\Big(\text{t}-\frac{\text{x}}{\text{c}}\Big)$
$\text{B}=\text{B}_0\sin\omega\Big(\text{t}-\frac{\text{x}}{\text{c}}\Big)$
The average value of either E or Bover a cycle is zero (average of $\sin(\theta)$ over a cycle is zero).
Also the electric energy density (UE) and magnetic energy density (UB)are equal.
$\text{u}_\text{E}=\frac{1}{2}\in_0\text{E}^2=\frac{\text{B}^2}{2\mu_0}=\text{u}_\text{B}$
Energy can be found out by integrating energy density over the entire volume of full space. As the energy of the electromagnetic wave is equally shared between electric and magnetic field so their average values will also be equal.
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A capacitor of capacitance 5
is connected as shown in the figure. The internal resistance of the cell is 0.5 Ω. The amount of charge on the capacitor plate is
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(a) 0 |
(b) 5 |
(c) 10 |
(d) 25 |
A galvanometer having a resistance of 8 ohm is shunted by a wire of resistance 2 ohm. If the total current is 1 amp, the part of it passing through the shunt will be
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(a) 0.25 amp |
(b) 0.8 amp |
(c) 0.2 amp |
(d) 0.5 amp |
Assertion : Through the same current flows through the line wires and the filament of the bulb but heat produced in the filament is much higher then that in line wires.
Reason : The filament of bulbs is made of a material of high resistance and high melting point.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true
|
(a) Its kinetic energy increases and its potential and total energies decrease |
|
(b) Its kinetic energy decreases, potential energy increases and its total energy remains the same |
|
(c) Its kinetic and total energies decrease and its potential energy increases |
|
(d) Its kinetic, potential and total energies decreases |
A ray of light is incidenting normally on a plane mirror. The angle of reflection will be
| (a) 0° | (b) 90° |
| (c) Will not be reflected | (d) None of the above |
The momentum of the photon of wavelength 5000Å will be
|
(a) 1.3 |
(b) 1.3 |
|
(c) 4 |
(d) 4 |
