Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from thecodes(a), (b), (c) and (d) as given below.
  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 and R is also false.
Assertion: The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decrease exponentially with increasing band gap.
Reason: It will be more difficult for the electron to cross over the large band gap while going from valence band to conduction band.

Answer

  1. Both A and R are true and R is the correct explanation of A.
Explanation:
For electron to jump from valence band to conduction band needs energy equal or more than the forbidden band between these two band. As the energy of band gap increases, it becomes difficult for electron to get that equivalent energy.

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For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
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Assertion: An electric lamp connected in series with a variable capacitor and A.C. source, its brightness increases with increase in capacitance.
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  2. Both A and R are true but R is not the correct explanation of A.
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Assertion: A convex lens of glass $(\mu = 1.5)$ behave as a diverging lens when immersed in carbon disulphide of higher refractive index $(\mu = 1.65).$
Reason: A diverging lens is thinner in the middle and thicker at the edges.
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Assertion (A): When the observation point lies along the length of the current element, magnetic field is zero.
Reason (R): Magnetic field close to current element is zero.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  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 and R is also false.
Assertion: Convergent lens property of converging remains same in all media.
Reason: Property of lens whether the ray is diverging or converging is independent of the surrounding medium.
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions front the codes (a), (b), (c) and (d) as given below.
  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.
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Assertion (A): Work function of aluminium is 4.2eV. Emission of electrons will not be possible if two photons each of energy 2.5eV strike an electron of aluminium.
Reason (R): For photoelectric emission the energy of each photon should be greater than the work function of aluminium.
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Assertion (A): The surface of a conductor is an equipotential surface.
Reason (R): Conductor allows the flow of charge.
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  2. Both A and R are true, but R is not the correct explanation of A.
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Assertion: Insulator do not allow flow of current through them.
Reason: Insulator have no free charge carrier.
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Assertion: The current in a wire is due to flow of free electrons in a definite direction.
Reason: A current carrying wire should have non-zero charge.
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Assertion: A person touching a high power line gets stuck with the line.
Reason: The current carrying wire attracts the man towards it.
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  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, and R is also false.
Assertion: The temperature coefficient of resistance is always positive only for metals.
Reason: On increasing the temperature, the resistance of metals and alloys increases.