When light passes from a denser to a rarer medium at an angle greater than the critical angle, what happens?
ALight refracts away from normal
BLight undergoes total internal reflection
CLight partially reflects and refracts
DLight is absorbed completely
Correct Answer:
B. Light undergoes total internal reflection
Explanation:
At critical angle θ_c, refracted ray becomes parallel to the interface. Beyond this angle, no refraction occurs; light completely reflects back into the denser medium (total internal reflection). This principle enables fiber optics.
A copper wire is stretched elastically. Which property is NOT affected?
AYoung's modulus
BElectrical resistivity
CLength
DCross-sectional area
Correct Answer:
A. Young's modulus
Explanation:
Young's modulus is a material property independent of the wire's dimensions or elastic deformation state. It depends only on the material composition and atomic structure, not on physical changes.
Which of the following statements about velocity is correct?
AVelocity is a scalar quantity that can never be negative
BVelocity is a vector quantity that includes both magnitude and direction
CVelocity and speed are always equal in magnitude
DVelocity remains constant in circular motion
Correct Answer:
B. Velocity is a vector quantity that includes both magnitude and direction
Explanation:
Velocity is a vector quantity with both magnitude and direction, unlike speed which is scalar. Velocity can be negative, and in circular motion, velocity constantly changes direction.
Which law of motion states that the acceleration of an object is directly proportional to the net force applied and inversely proportional to its mass?
ANewton's First Law
BNewton's Second Law
CNewton's Third Law
DLaw of Universal Gravitation
Correct Answer:
B. Newton's Second Law
Explanation:
Newton's Second Law: F = ma, where acceleration is directly proportional to force and inversely proportional to mass.
Two identical objects moving with velocities v and 2v collide and stick together. What fraction of kinetic energy is lost?
A1/3
B2/3
C1/2
D2/5
Correct Answer:
B. 2/3
Explanation:
Initial KE = ½m(v)² + ½m(2v)² = 2.5mv². Final velocity = 3v/2 (by momentum conservation). Final KE = ½(2m)(3v/2)² = 2.25mv²/4 = 0.84mv². Loss = 2.5 - 0.84 = 1.66, which is 2/3 of initial KE.