SSC CGL Science – Light & Optics – Level 3 · Challenge

← Back

SSC CGL Science – Light & Optics – Level 3 · Challenge – 8 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

Get daily current affairs & exam alerts – follow us YouTube WhatsApp Channel Telegram Channel Facebook Page Instagram
Share with friends & study groups
Link to this page from your website / blog (HTML code)
1.  
A convex lens of power +4 D and a concave lens of power −1.5 D are placed in contact. The focal length of the combination is:

Correct Answer: A [40 cm]

Explanation:

P = 2.5 D → f = 100/2.5 = 40 cm.

2.  
A man runs towards a plane mirror at 2 m/s. His image approaches him at:

Correct Answer: C [4 m/s]

Explanation:

The image moves at 2 m/s towards the mirror too, so the image approaches the man at 2 + 2 = 4 m/s.

3.  
The minimum length of a plane mirror needed for a 1.8 m tall person to see his full image is:

Correct Answer: D [0.9 m]

Explanation:

Answer: 0.9 m. Half the height.

4.  
Spot My Mistake“Light bends towards the normal when it goes from glass into air.” The correct statement is:

Correct Answer: A [It bends away from the normal going from glass (denser) into air (rarer)]

Explanation:

Denser → rarer: away from the normal.

5.  
A doctor prescribes a lens of +2.0 D to an old person for reading. The lens is:

Correct Answer: B [convex, focal length 50 cm]

Explanation:

100/2 = +50 cm; presbyopia needs a plus lens.

6.  
An object is placed 12 cm in front of a concave mirror of focal length 8 cm. The image is formed:

Correct Answer: C [24 cm in front of the mirror, enlarged and inverted]

Explanation:

1/v = −1/8 + 1/12 = −1/24 → v = −24 cm, m = −v/u = −2.

7.  
Which pair is correctly matched?

Correct Answer: C [Cataract – opaque eye lens]

Explanation:

Cataract clouds the lens and is treated by surgery.

8.  
Reverse questionThe answer is “Tyndall effect”. Which observation does it explain?

Correct Answer: D [A beam of sunlight becomes visible in a dusty, smoky room]

Explanation:

Colloidal particles scatter light and show its path.

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science

📘 SSC CGL 2026 – General Science (Tier I + Tier II)
Here you get the answer with a one-line explanation. 1,110 original questions with answer key and explanations · mind-maps, notes, tables and shortcuts · Tier I and Tier II practice sets + 3 mock tests
Get the book – ₹149 ₹299 →
Score: 0 Answered: 0 / 0