SSC CGL Science – Modern Physics, Electronics & Everyday Devices – Level 2 · Exam Level · Tier I Sprint

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SSC CGL Science – Modern Physics, Electronics & Everyday Devices – Level 2 · Exam Level · Tier I Sprint – 15 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.  
Using E (eV) ≈ 1240 ÷ λ (nm), the energy of an ultraviolet photon of wavelength 248 nm is about:

Correct Answer: C [5.0 eV]

Explanation:

Answer: 5.0 eV. 1240 ÷ 248 = 5.0 eV.

2.  
Match the followingMatch the reactor part with a material used for it:
P. Moderator Q. Control rods R. Coolant (fast breeder)
1. Boron 2. Graphite 3. Liquid sodium

Correct Answer: A [P-2, Q-1, R-3]

Explanation:

Graphite slows neutrons; boron absorbs them; liquid sodium carries heat in fast breeders.

3.  
Radium-226 (Z = 88) emits one alpha particle. The new nucleus is:

Correct Answer: B [Radon-222 (Z = 86)]

Explanation:

α lowers A by 4 and Z by 2: 226 → 222, 88 → 86 (radon).

4.  
Odd one outWhich of these is NOT an electromagnetic wave?

Correct Answer: D [Ultrasound]

Explanation:

Ultrasound is a sound (mechanical) wave; the others are EM waves.

5.  
In the photoelectric effect (frequency above threshold), increasing only the intensity of light increases the:

Correct Answer: C [number of photoelectrons emitted per second]

Explanation:

Intensity = number of photons → more electrons; their maximum KE depends on frequency only.

6.  
Assertion–Reason
A: An n-type silicon crystal is electrically neutral.
R: Each donor atom that gives a free electron becomes a positive ion fixed in the lattice.

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

Explanation:

Free electrons are balanced by the fixed positive donor ions, so the crystal is neutral.

7.  
For which input pair (A, B) is the output of a NOR gate equal to 1?

Correct Answer: D [(0, 0)]

Explanation:

NOR = NOT(OR); OR is 0 only when both inputs are 0.

8.  
Chronological orderarrange from earliest to latest.
1. Discovery of the neutron 2. Discovery of X-rays 3. Discovery of the electron 4. Bohr's model of the atom

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

Explanation:

X-rays 1895 → electron 1897 → Bohr 1913 → neutron 1932.

9.  
The three terminals of a bipolar junction transistor are:

Correct Answer: B [emitter, base and collector]

Explanation:

A bipolar transistor has emitter, base and collector.

10.  
Which device converts alternating current (AC) into direct current (DC)?

Correct Answer: C [Rectifier]

Explanation:

Diode rectifiers allow current one way only, giving DC.

11.  
Two-quantity comparison
Quantity I: energy (eV) of one photon of wavelength 620 nm
Quantity II: total energy (eV) of two photons of wavelength 1240 nm

Correct Answer: A [Quantity I = Quantity II]

Explanation:

1240/620 = 2 eV; two photons of 1240/1240 = 1 eV each = 2 eV.

12.  
An MRI scanner forms images using:

Correct Answer: D [a strong magnetic field and radio waves]

Explanation:

MRI uses a magnet and radio waves; CT uses X-rays; sonography uses ultrasound.

13.  
Fill in the blankIn a nuclear reactor, the ___ slows down fast neutrons so that they can cause fission.

Correct Answer: C [moderator]

Explanation:

Moderator (heavy water/graphite) slows; control rods absorb; coolant removes heat.

14.  
Spot My Mistake“U-238 (Z = 92) emits one β⁻ particle, so its mass number becomes 237 and Z becomes 93.” What is the correct product?

Correct Answer: D [A = 238, Z = 93 (Neptunium)]

Explanation:

β⁻ emission does not change A; Z rises by 1 → ²³⁸₉₃Np.

15.  
True/false countHow many of these statements are true?
I. Gamma rays have the highest frequency in the EM spectrum.
II. Radio waves have the longest wavelength.
III. Visible light lies between infrared and ultraviolet.
IV. Microwaves travel faster than X-rays in vacuum.

Correct Answer: A [3]

Explanation:

I, II, III are true; all EM waves have the same speed in vacuum, so IV is false.

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