SSC CGL Science – Modern Physics, Electronics & Everyday Devices – Tier II Level · Marathon

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SSC CGL Science – Modern Physics, Electronics & Everyday Devices – Tier II Level · Marathon – 10 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.

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1.  
If 1 mg of matter is completely converted into energy, the energy released is (c = 3 × 10⁸ m/s):

Correct Answer: C [9 × 10¹⁰ J]

Explanation:

E = mc² = 10⁻⁶ kg × 9 × 10¹⁶ = 9 × 10¹⁰ J.

2.  
The energy of the photon emitted when the electron in a hydrogen atom jumps from n = 2 to n = 1 is:

Correct Answer: C [10.2 eV]

Explanation:

Answer: 10.2 eV. 13.6 (1 − 1/4) = 10.2 eV.

3.  
1/16 of a radioactive sample remains after 20 days. Its half-life is:

Correct Answer: D [5 days]

Explanation:

1/16 = 1/2⁴ → 4 half-lives in 20 days → 5 days each.

4.  
A piece of old wood has 1/4 of the carbon-14 found in living wood. Taking the half-life of C-14 as 5,730 years, its age is about:

Correct Answer: A [11,460 years]

Explanation:

1/4 = 2 half-lives → 2 × 5,730 = 11,460 years.

5.  
Assertion–Reason
A: Shining light on a reverse-biased photodiode increases the reverse current.
R: Absorbed photons create electron–hole pairs near the junction.

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

Explanation:

Extra carriers made by light raise the reverse current – the working principle of a photodiode.

6.  
In β⁻ decay, what happens inside the nucleus?

Correct Answer: A [A neutron changes into a proton and an electron is emitted]

Explanation:

n → p + e⁻ (+ antineutrino): Z rises by 1, A unchanged.

7.  
A NOR gate whose two inputs are joined together behaves as a:

Correct Answer: D [NOT gate]

Explanation:

NOR(A, A) = NOT(A) – one reason NOR is a universal gate.

8.  
Two-quantity comparison
Quantity I: number of neutrons in ²²²₈₆Rn
Quantity II: number of neutrons in ²²⁶₈₈Ra

Correct Answer: B [Quantity I < Quantity II]

Explanation:

Rn: 222 − 86 = 136; Ra: 226 − 88 = 138 (an α takes away 2 neutrons).

9.  
An electron microscope shows much finer detail than an optical microscope mainly because:

Correct Answer: C [the de Broglie wavelength of fast electrons is much shorter than that of visible light]

Explanation:

Resolution improves with shorter wavelength; λ = h/mv for electrons is far below 400 nm.

10.  
Chronological orderChronological order (earliest first):
1. de Broglie's matter waves 2. Planck's quantum idea 3. Bohr's atomic model 4. Einstein's explanation of the photoelectric effect

Correct Answer: C [2, 4, 3, 1]

Explanation:

Planck 1900 → Einstein 1905 → Bohr 1913 → de Broglie 1924.

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

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