Showing 41–50 of 96 questions
The refractive index of a medium is 1.5. What is the speed of light in that medium? (c = 3 × 10⁸ m/s)
A
1.5 × 10⁸ m/s
B
2 × 10⁸ m/s
C
2.5 × 10⁸ m/s
D
3 × 10⁸ m/s
Correct Answer:
B. 2 × 10⁸ m/s
Explanation:
Refractive index n = c/v. Therefore, v = c/n = (3 × 10⁸)/1.5 = 2 × 10⁸ m/s.
Which of the following elements has an electronic configuration of 2, 8, 7?
A
Chlorine
B
Bromine
C
Fluorine
D
Iodine
Correct Answer:
A. Chlorine
Explanation:
Chlorine (Cl) has atomic number 17, with electronic configuration 2, 8, 7 (K-shell: 2, L-shell: 8, M-shell: 7).
A car moving at 72 km/h applies brakes and comes to rest in 8 seconds. What is the deceleration?
A
2.5 m/s²
B
2.0 m/s²
C
1.5 m/s²
D
3.0 m/s²
Correct Answer:
A. 2.5 m/s²
Explanation:
First convert 72 km/h = 20 m/s. Using v = u + at: 0 = 20 + a(8), so a = -20/8 = -2.5 m/s². Magnitude of deceleration is 2.5 m/s².
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
A current-carrying conductor is placed in a magnetic field perpendicular to it. What force acts on it?
A
Gravitational force
B
Lorentz force
C
Electrostatic force
D
Frictional force
Correct Answer:
B. Lorentz force
Explanation:
The force on a current-carrying conductor in a magnetic field is called the Lorentz force, given by F = BIL
A transformer has 500 turns in primary and 100 turns in secondary coil. If primary voltage is 220V, what is the secondary voltage?
A
44 V
B
1100 V
C
22 V
D
110 V
Explanation:
Using transformer equation Vs/Vp = Ns/Np, we get Vs = 220 × (100/500) = 44 V
An object is placed 30 cm in front of a concave mirror with focal length 10 cm. Where is the image formed?
A
15 cm behind the mirror
B
15 cm in front of the mirror
C
20 cm in front of the mirror
D
20 cm behind the mirror
Correct Answer:
A. 15 cm behind the mirror
Explanation:
Using mirror formula 1/f = 1/u + 1/v, where f = -10 cm, u = -30 cm, we get v = -15 cm (behind mirror)
