SSC CGL Science – Light & Optics – Tier II Level · Marathon

← Back

SSC CGL Science – Light & Optics – Tier II Level · Marathon – 11 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.  
An object is 20 cm from a convex lens of focal length 10 cm. The image distance is:

Correct Answer: A [20 cm on the other side]

Explanation:

Answer: 20 cm on the other side. 1/v = 1/10 − 1/20 = 1/20.

2.  
An object is 20 cm in front of a convex mirror of focal length 15 cm. The image is about:

Correct Answer: B [8.6 cm behind the mirror, erect and diminished]

Explanation:

1/v = 1/15 + 1/20 = 7/60 → v ≈ 8.57 cm; m ≈ 0.43.

3.  
A concave lens of focal length 15 cm forms an image of an object placed 30 cm from it. The magnification is:

Correct Answer: A [+1/3]

Explanation:

1/v = −1/15 − 1/30 = −1/10 → v = −10 cm; m = v/u = 1/3.

4.  
A ray passes from water (n = 4/3) into glass (n = 3/2) at an angle of incidence whose sine is 0.6. The sine of the angle of refraction is:

Correct Answer: D [0.533]

Explanation:

n₁ sin i = n₂ sin r → sin r = (4/3)(0.6)/(3/2) = 0.533.

5.  
The critical angle for a medium is 30°. Its refractive index is:

Correct Answer: C [2]

Explanation:

Answer: 2. n = 1/sin 30° = 2.

6.  
A telescope has an objective of focal length 100 cm and an eyepiece of 5 cm. Its magnifying power in normal adjustment is:

Correct Answer: B [20]

Explanation:

Answer: 20. m = f₀/fₑ = 100/5.

7.  
The length of the same telescope tube in normal adjustment is:

Correct Answer: C [105 cm]

Explanation:

Answer: 105 cm. L = f₀ + fₑ.

8.  
A magnifying glass of focal length 5 cm forms the final image at 25 cm. Its magnifying power is:

Correct Answer: A [6]

Explanation:

Answer: 6. m = 1 + D/f = 1 + 25/5.

9.  
The radius of curvature of a concave mirror is 40 cm. Its focal length (Cartesian sign convention) is:

Correct Answer: D [−20 cm]

Explanation:

f = R/2 = 20 cm; concave → negative.

10.  
Assertion–ReasonAssertion (A): A real image formed by a single convex lens is always inverted.
Reason (R): For a real image, v and u have opposite signs, so m = v/u is negative.

Correct Answer: B [Both A and R are true and R explains A]

Explanation:

Real ⇔ inverted for a single lens.

11.  
Data tableFor a convex lens – object distance (cm): 30, 20, 15; image distance (cm): 15, 20, 30. The focal length of the lens is:

Correct Answer: B [10 cm]

Explanation:

1/f = 1/v + 1/|u| = 1/15 + 1/30 = 1/10 for every row.

➤ 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