Q.36 Physics · Section B ⭐ 360° Option Elimination Active

NEET 2024 Physics Question 36 Solution

Topic: Ray Optics and Optical Instruments · Official NTA Booklet Code T1

Question

A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm. The magnifying power of telescope for viewing a distant object is:

✓

Verified Against NTA Final Answer Key

Option (4) : 28

📚 Ray Optics and Optical Instruments Easy

📋 Given Parameters & Problem Setup

Objective focal length f_o = 140 cm

Eyepiece focal length f_e = 5.0 cm

Object Distant object (normal adjustment)

⚡

The 30-Second Exam Hall Shortcut: ⚡ Normal Adjustment Telescope Shortcut

⏱️ Save ~30 seconds

Magnifying power m = f_o / f_e = 140 / 5.0 = 28!

1 For viewing distant objects in normal adjustment (image formed at infinity), magnifying power of telescope is m = f_o / f_e.

2 Substitute given values: f_o = 140 cm and f_e = 5.0 cm.

3 m = 140 / 5.0 = 28.

4 Option (4) in under 3 seconds!

🛡️

Why You Can 100% Trust This Shortcut: Astronomical Telescope Magnifying Power Formula in Normal Adjustment (m = f_o / f_e).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Formula for Magnifying Power of an Astronomical Telescope

For an astronomical refracting telescope viewing a distant celestial object under normal adjustment (relaxed eye, final image at infinity), the angular magnification m is given by the ratio of the focal length of the objective lens to that of the eyepiece lens:

m = \frac{f_o}{f_e}

Step 2

Substitution and Evaluation

Substituting f_o = 140 cm and f_e = 5.0 cm:

m = \frac{140\,\text{cm}}{5.0\,\text{cm}} = 28

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✗ Incorrect

Verdict & Scientific Reason:

Arbitrary incorrect value.

⚠️

Student Fallacy (Why candidates pick this trap): Arithmetic miscalculation.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Incorrect division.

⚠️

Student Fallacy (Why candidates pick this trap): Rough guessing.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Incorrect.

⚠️

Student Fallacy (Why candidates pick this trap): Division slip.

4 (4)

✓ 100% Correct

Verdict & Scientific Reason:

Exact quotient: 140 / 5 = 28.

💡

Why this is airtight: None.

⚠️

NTA Trap Alert: Inverting Objective and Eyepiece

Students who confuse microscope and telescope formulas sometimes divide f_e by f_o, getting a fraction < 1.

🛡️ How to avoid the -1 mark: Telescope OBJECTIVE is always huge (large f_o) to gather light from distant stars; Eyepiece is small (small f_e). Hence m = f_o / f_e >> 1.

📖

Core NEET Syllabus Standard

Physics Core Optics · Ray Optics and Optical Instruments Standard Benchmark

Core Scientific Principle Tested:

"The magnifying power of an astronomical telescope in normal adjustment is m = f_o / f_e."

Syllabus Focus: Refracting Telescopes

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Telescope: Big f_o over tiny f_e: 140 / 5 is 28 to see!

Ready to attempt under real exam pressure?

Test your speed and accuracy in the authentic 200-minute timed NTA simulator.

Launch NEET 2024 CBT Test →

← Previous (Q.35) All Physics Questions Grid Next (Q.37) →

Spotted a mistake in this solution? Report an error ([email protected])

⚖️ Legal & Fair Dealing Notice: Sourced from publicly released NEET 2024 question papers and NEET answer keys for private study, research, and non-commercial educational practice under Fair Dealing (Section 52(1)(a) of the Indian Copyright Act, 1957). Not affiliated with or endorsed by NTA or NMC.

NEET 2024 Physics Question 36 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Normal Adjustment Telescope Shortcut

Step-by-Step Rigorous Workflow & Mathematical Proof

Formula for Magnifying Power of an Astronomical Telescope

Substitution and Evaluation

360° Option Elimination Engine Key Feature

NTA Trap Alert: Inverting Objective and Eyepiece

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Ray Optics and Optical Instruments

Apparent Depth Calculations Across Multi-Layer Dielectric Media

Two-Lens System Image Formation with Convex and Concave Lenses

Compound Microscope Magnification at Normal Adjustment

Combination of Lenses in Contact: Power and Magnification

Solve 4 NEET Questions a Day — One per Subject