Assertion: Intensity of magnetic field due to a solenoid near its ends is only half of its magnitude inside the solenoid.
Reason: If solenoid is made very long then magnetic field inside the solenoid becomes uniform.

Options

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

Answer

B

Explanation

Magnetic field inside solenoid `B = mu_(0)ni`. It is independent of length and area of cross-section. Hence the assertion is true.
Reason is also true. But it does not explain the assertion.