The colour of an object is due to MCQ with Answer and Explanation

The colour of an object is due to
A. Absorption of all colours
B. Reflection of that colour
C. Emission of that colour
D. Transmission of that colour
Answer: Option B
Solution (By JKSSB Mock Tests)
Object reflects that colour and absorbs others.

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Practice More Physics Questions

Question #1
An artificial satellite orbits Earth in a circular path. If its orbital radius is increased, its orbital velocity:
A. Increases
B. Decreases
C. Becomes zero
D. Remains constant

Correct Answer: Option B


Explanation:
Orbital velocity v = √(GM/r), where r is orbital radius from Earth's center. Thus v ∝ 1/√r. If r increases, v decreases. This follows from equating gravitational force to centripetal force: GMm/r² = mv²/r ⇒ v = √(GM/r). Higher orbits have slower speeds but longer periods. Memory aid: 'Higher orbit, slower speed' – counterintuitive but fundamental. This relationship is crucial for satellite motion questions in competitive exams. Always distinguish orbital velocity from escape velocity (which is √2 times orbital velocity at same radius).

This question belongs to: Science Physics
Question #2
Ohm's law is valid for
A. Electrolytes
B. Semiconductors only
C. Metallic conductors at constant temperature
D. All conductors

Correct Answer: Option C


Explanation:
Ohm's law V = IR holds for ohmic conductors (metals) provided temperature and physical conditions constant. Non-ohmic: semiconductors, diodes, electrolytes. Graph V-I is straight line for ohmic. Temperature changes resistance, so condition necessary.

This question belongs to: Science Physics
Question #3
A machine does 500 J of work in 10 seconds. Its power is
A. 5000 W
B. 5 W
C. 50 W
D. 0.5 W

Correct Answer: Option C


Explanation:
Power = work/time = 500/10 = 50 W. Watt = Joule/second. This is average power. Simple division. Higher power means faster rate of doing work.

This question belongs to: Science Physics