Which of the following is NOT a vector quantity?
A
Displacement
B
Temperature
C
Velocity
D
Acceleration
Correct Answer:
B. Temperature
Explanation:
Temperature is a scalar quantity as it has only magnitude. Displacement, velocity, and acceleration are vector quantities as they have both magnitude and direction.
A charged particle moves in a magnetic field. Under what condition does it move in a straight line?
A
Velocity is parallel to magnetic field
B
Velocity is perpendicular to magnetic field
C
Magnetic field is very strong
D
Particle has positive charge
Correct Answer:
A. Velocity is parallel to magnetic field
Explanation:
Lorentz force F = q(v × B). When v is parallel to B, the cross product is zero, so no force acts
Which phenomenon causes the sky to appear blue during daytime?
A
Reflection of light
B
Refraction of light
C
Rayleigh scattering
D
Total internal reflection
Correct Answer:
C. Rayleigh scattering
Explanation:
Blue light has shorter wavelength and is scattered more by atmospheric molecules (Rayleigh scattering)
A wire of resistance R is stretched to double its length. What is the new resistance?
Explanation:
Resistance R = ρL/A. When length doubles, L becomes 2L and area becomes A/2 (volume constant). New R = ρ(2L)/(A/2) = 4ρL/A = 4R
Which quantum number determines the shape of an orbital?
A
Principal quantum number (n)
B
Azimuthal quantum number (l)
C
Magnetic quantum number (m)
D
Spin quantum number (s)
Correct Answer:
B. Azimuthal quantum number (l)
Explanation:
The azimuthal quantum number (l) determines the shape of the orbital (s, p, d, f)
A convex lens of focal length 20 cm is used as a magnifying glass. If an object is placed 5 cm from the lens, what is the nature of the image?
A
Real, inverted, diminished
B
Virtual, erect, magnified
C
Real, erect, diminished
D
Virtual, inverted, magnified
Correct Answer:
B. Virtual, erect, magnified
Explanation:
When object is between lens and focus (u < f), a convex lens produces virtual, erect, magnified image
What is the young's modulus of a material?
A
Stress/Strain
B
Strain/Stress
C
Force × Area
D
Force/Volume
Correct Answer:
A. Stress/Strain
Explanation:
Young's modulus Y = Stress/Strain = (F/A)/(ΔL/L), a measure of material stiffness
Which statement about elastic collisions is correct?
A
Momentum is not conserved
B
Kinetic energy is conserved
C
Objects always stick together
D
Maximum energy is lost
Correct Answer:
B. Kinetic energy is conserved
Explanation:
In elastic collisions, both momentum and kinetic energy are conserved
A radioactive element has a half-life of 10 years. After 30 years, what fraction of the original sample remains?
Explanation:
After 3 half-lives (30 years), the fraction remaining = (1/2)³ = 1/8
Which of the following has the lowest refractive index?
A
Water
B
Glass
C
Air
D
Diamond
Explanation:
Air has a refractive index of approximately 1, which is the lowest among common materials
