Showing 71–79 of 79 questions
Which of the following statements about entropy is correct?
A
Entropy always decreases in an isolated system
B
Entropy is a measure of disorder and always increases in an isolated system
C
Entropy has no relation to the direction of chemical reactions
D
Entropy can be negative in physical systems
Correct Answer:
B. Entropy is a measure of disorder and always increases in an isolated system
EXPLANATION
According to the Second Law of Thermodynamics, entropy (disorder) of an isolated system always increases over time.
Which type of lens is used to correct myopia (short-sightedness)?
A
Convex lens
B
Concave lens
C
Bifocal lens
D
Cylindrical lens
Correct Answer:
B. Concave lens
EXPLANATION
Concave lenses are used to correct myopia by diverging light rays to focus them correctly on the retina.
What is the Doppler effect primarily related to?
A
Change in density
B
Change in frequency or wavelength of waves due to relative motion
C
Change in amplitude
D
Change in intensity
Correct Answer:
B. Change in frequency or wavelength of waves due to relative motion
EXPLANATION
The Doppler effect describes the change in frequency or wavelength of waves when the source or observer moves relative to each other.
Which of the following is an example of a heterogeneous mixture?
A
Salt solution
B
Sugar solution
C
Sand and iron filings
D
Alcohol and water
Correct Answer:
C. Sand and iron filings
EXPLANATION
Sand and iron filings form a heterogeneous mixture as their components remain visibly distinct and can be easily separated.
In the context of railways, which type of braking system provides the fastest stopping power?
A
Air brake
B
Hydraulic brake
C
Regenerative brake
D
Magnetic brake
Correct Answer:
D. Magnetic brake
EXPLANATION
Magnetic brakes provide rapid and controlled stopping. Regenerative brakes are energy-efficient but slower. Air/hydraulic are conventional systems.
The theory that explains the motion of planets around the sun is:
A
Newton's First Law
B
Kepler's Laws of Planetary Motion
C
Law of Conservation of Energy
D
Coulomb's Law
Correct Answer:
B. Kepler's Laws of Planetary Motion
EXPLANATION
Kepler's Laws of Planetary Motion describe how planets orbit the sun in elliptical paths with the sun at one focus.
Which element is the most abundant in the Earth's crust?
A
Iron
B
Oxygen
C
Silicon
D
Aluminum
Correct Answer:
B. Oxygen
EXPLANATION
Oxygen is the most abundant element in Earth's crust, comprising about 46% of its composition.
The phenomenon where light bends while passing from one medium to another is called:
A
Reflection
B
Refraction
C
Diffraction
D
Dispersion
Correct Answer:
B. Refraction
EXPLANATION
Refraction is the bending of light when it passes from one transparent medium to another with different optical density.
Which of the following is a vector quantity?
A
Speed
B
Temperature
C
Velocity
D
Distance
Correct Answer:
C. Velocity
EXPLANATION
Velocity is a vector quantity as it has both magnitude and direction. Speed, temperature, and distance are scalar quantities.
