Q.11
Hard
Which gas is used in welding and cutting of metals?
A
Nitrogen
B
Oxygen
C
Acetylene
D
Hydrogen
Correct Answer:
C. Acetylene
Explanation:
Acetylene (C₂H₂) is commonly used in oxy-acetylene welding and cutting due to its high flame temperature of about 3,300°C.
Q.12
Hard
At what temperature do Celsius and Fahrenheit scales show the same reading?
Explanation:
At -40°, both Celsius and Fahrenheit scales show the same value: -40°C = -40°F.
Q.13
Hard
What is the half-life of Carbon-14, which is used in radioactive dating?
A
573 years
B
5,730 years
C
57,300 years
D
573,000 years
Correct Answer:
B. 5,730 years
Explanation:
Carbon-14 has a half-life of approximately 5,730 years, making it useful for dating archaeological artifacts.
Q.14
Hard
Which of the following correctly represents the order of electromagnetic spectrum from lowest to highest frequency?
A
Radio, microwave, visible, X-ray, gamma
B
Gamma, X-ray, visible, microwave, radio
C
Visible, radio, microwave, X-ray, gamma
D
X-ray, visible, radio, gamma, microwave
Correct Answer:
A. Radio, microwave, visible, X-ray, gamma
Explanation:
The electromagnetic spectrum in order of increasing frequency: Radio < Microwave < Infrared < Visible < Ultraviolet < X-ray < Gamma.
Q.15
Hard
What is the focal length of a plane mirror?
A
Zero
B
Infinity
C
Equal to radius of curvature
D
Half the radius
Correct Answer:
B. Infinity
Explanation:
A plane mirror has infinite focal length because it does not converge or diverge light rays.
Q.16
Hard
According to the Doppler effect, what happens to the frequency of sound when a source moves towards an observer?
A
Frequency decreases
B
Frequency increases
C
Frequency remains constant
D
Frequency becomes zero
Correct Answer:
B. Frequency increases
Explanation:
The Doppler effect causes the observed frequency to increase when a sound source moves towards the observer due to compression of sound waves.
Q.17
Hard
Which law of thermodynamics states that energy cannot be created or destroyed?
A
First law of thermodynamics
B
Second law of thermodynamics
C
Third law of thermodynamics
D
Zeroth law of thermodynamics
Correct Answer:
A. First law of thermodynamics
Explanation:
The First Law of Thermodynamics is the Law of Conservation of Energy, which states that energy is neither created nor destroyed but only transformed.
Q.18
Hard
Which of the following statements about sound waves is incorrect?
A
Sound travels faster in solids than in air
B
Sound requires a medium to propagate
C
Sound can propagate through vacuum
D
Frequency of sound determines its pitch
Correct Answer:
C. Sound can propagate through vacuum
Explanation:
Sound cannot propagate through vacuum because it requires a medium (solid, liquid, or gas) to travel. Sound travels fastest in solids, slower in liquids, and slowest in gases. Frequency determines pitch.
Q.19
Hard
Which of the following elements has the highest electronegativity according to the Pauling scale?
A
Oxygen
B
Chlorine
C
Fluorine
D
Nitrogen
Correct Answer:
C. Fluorine
Explanation:
Fluorine has the highest electronegativity value (3.98) on the Pauling scale. Electronegativity is the tendency of an atom to attract electrons in a chemical bond. As we go from fluorine down the halogen group, electronegativity decreases.
Q.20
Hard
Which of the following exhibits both wave and particle properties?
A
Sound waves only
B
Light only
C
Light and electrons
D
Water waves only
Correct Answer:
C. Light and electrons
Explanation:
Light and electrons exhibit wave-particle duality, meaning they behave as both waves and particles depending on the experiment.
