CUET · PHYSICS · PYQ PAPER 2023

Electric field intensity at a point varies as \( \frac{1}{r^3} \) due to:

A a point charge
B a short electric dipole
C a line charge of infinite length
D a plane infinite sheet of charge

Verified Solution

Answer & Solution

Correct Answer

(B) a short electric dipole

Step-by-step Solution

Detailed explanation

For a short electric dipole, the electric fields from the positive and negative charges partially cancel each other out, causing the intensity to drop faster than a point charge. Specifically, it follows the relationship \(E \propto 1 / r ^{ 3 }\). B) a short electric dipole

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match List-I with List-II

List-I (Optical instrument)	List-II (Magnifying power)
(A) Magnifying power m of a simple microscope	(I) \( m = 1 + (D/f) \)
(B) Magnifying power m of a simple microscope if the image is at infinity	(II) \( m = (L/f_0) \times (D/f_e) \)
(C) Magnifying power m of a compound microscope	(III) \( m = f_0 / f_e \)
(D) Magnifying power m of a telescope	(IV) \( m = D/f \)

Choose the correct answer from the options given below:

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