If the length and area of cross-section of a conductor are doubled, then its resistance will be
1. unchanged
2. halved
3. doubled
4. quadrupled
If the length and area of cross-section of a conductor are doubled, then its resistance will be
1. unchanged
2. halved
3. doubled
4. quadrupled
Subtopic: Derivation of Ohm's Law |
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A source of light lies on the angle bisector of two plane mirrors inclined at angle θ. The values of θ, so that the light reflected from one mirror does not reach the other mirror will be
1. 
4. None of the above
Subtopic: Reflection at Plane Surface |
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A ruby laser produces radiations of wavelengths, 662.6 nm in pulse whose duration are 10–9 s. If the laser produces 0.39 J of energy per pulse, how many photons are produced in each pulse?
1. 1.3 × 109
Subtopic: Photoelectric Effect: Experiment |
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Balmer gives an equation for wavelength of visible radiation of H– spectrum as \(\lambda=\frac{k n^{2}}{n^{2}-4}\). The value of k in terms of Rydberg’s constant R is
1. R
2. 4R
3. \(R \over 4\)
4. \(4 \over R\)
Subtopic: Spectral Series |
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From NCERT
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and 
are electron and hole mobility, E be the applied electric field, the current density 
for intrinsic semiconductor is equal to
Three charged particles are collinear and are in equilibrium, then
1. All the charged particles have the same polarity
2. The equilibrium is unstable
3. All the charged particles cannot have the same polarity
4. Both (b) and (c) are correct
Subtopic: Coulomb's Law |
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Given below are two statements:
| Assertion (A): | Mass of moving photons varies inversely as the wavelength. |
| Reason (R): | The energy of the particle = Mass × (speed of light)2. |
| 1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 3. | (A) is true but (R) is false. |
| 4. | (A) is false but (R) is true. |
Subtopic: Photoelectric Effect: Experiment |
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Assertion A hollow metallic closed container maintained at a uniform temperature can act as a source of a black body radiation.
Reason All metals act as a black body.
Reason All metals act as a black body.
1. If both assertion and reason are true and reason explain the assertion.
2. If both the assertion and reason are true but reason does not explain the assertion.
3. If assertion is true but reason is false.
4. If assertion is false but reason is true.
Subtopic: Radiation |
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