Nmdcat Practice Paper from PMDC Syllabus | mosaicbro.com
Nmdcat Practice Paper from PMDC Syllabus
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Review Answers:
148
The ratio of largest to shortest wavelength in Lyman series of hydrogen atom is:
Correct Answer:A
Explanation:
The Lyman series involves transitions to the n=1 level. The largest wavelength corresponds to the transition from n=2 to n=1, and the shortest wavelength corresponds to the transition from n=∞ to n=1. The ratio is calculated as (1/(1-1/4))/(1/(1-1/∞)) = 4/3.
149
Which of the following is true?
Correct Answer:B
Explanation:
The Paschen series involves transitions to the n=3 level and is observed in the infrared region of the spectrum.
150
What is the role of electrons in an atom?
Correct Answer:C
Explanation:
Electrons are involved in chemical bonding and determine the chemical properties of an element.
151
What determines the atomic number of an element?
Correct Answer:B
Explanation:
The atomic number of an element is determined by the number of protons in its nucleus.
152
The phenomena of spontaneous disintegration of heavier elements (Z>82) into lighter nuclei with the emission of three types of radiation is:
Correct Answer:A
Explanation:
Radioactivity is the spontaneous disintegration of unstable atomic nuclei, typically emitting alpha, beta, or gamma radiation.
153
Which of the following radiations is most dangerous inside the body?
Correct Answer:A
Explanation:
Alpha particles are highly ionizing and can cause significant damage if ingested or inhaled, despite their low penetration power.
154
A 200 g radioactive sample decays to 25 g in 3 hours. What is its half-life?
Correct Answer:C
Explanation:
The sample decays to 1/8th of its original mass in 3 hours, which corresponds to 3 half-lives (since 1/2^3 = 1/8). Thus, the half-life is 1 hour (60 minutes).