(A): In an N type semiconductor fermi level shifts towards conduction band
(R) : Donor impurities are present in N-type semi conductor.

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'
B. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'
C. 'A' is true and 'R' is false
D. 'A' is false and 'R' is true

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided in the context of N-type semiconductors.

### Step 1: Understand the Assertion (A)
The assertion states that in an N-type semiconductor, the Fermi level shifts towards the conduction band.

**Explanation**:
In N-type semiconductors, donor impurities (like phosphorus or arsenic) are added to the intrinsic semiconductor (like silicon). These donor atoms have more valence electrons than the semiconductor material, which leads to the creation of additional free electrons. The presence of these free electrons increases the electron concentration in the conduction band, causing the Fermi level to shift closer to the conduction band.

### Step 2: Understand the Reason (R)
The reason states that donor impurities are present in N-type semiconductors.

**Explanation**:
This statement is true because N-type semiconductors are specifically created by doping an intrinsic semiconductor with donor impurities. These impurities donate extra electrons to the conduction band, which is a defining characteristic of N-type semiconductors.

### Step 3: Determine the Relationship between A and R
Now, we need to determine if the reason (R) correctly explains the assertion (A).

**Analysis**:
Since the presence of donor impurities in N-type semiconductors leads to an increase in free electrons, which in turn causes the Fermi level to shift towards the conduction band, we can conclude that the reason does indeed explain the assertion.

### Conclusion
Both the assertion (A) and the reason (R) are true, and the reason is the correct explanation of the assertion. Therefore, the answer is:

**Option 1: Both A and R are true, and R is the correct explanation of A.**

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