2025 · Paper 1

Complete GATE PH 2025 Paper 1 overview, original pages and practice · Timed previous-paper practice

Questions 28–30 of 65. Imported answers require review unless explicitly marked reviewed.

Question 28

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PHMSQ1 markNeeds review

Potential energy of two diatomic molecules P and Q of the same reduced mass is shown in the figure. According to this diagram, which of the following option(s) is/are correct?



Your answerSelect all correct options. You can choose more than one.

A.

The equilibrium inter-nuclear distance of Q is more than that of P

B.

The total energy



separates bound and unbound states of the molecules

C.

The lowest vibrational frequency of P is larger than that of Q

D.

Dissociation energy of Q is more than that of P

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Question 29

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PHMSQ1 markNeeds review

Nuclear radiation emitted from a



radioactive source is detected by a photomultiplier tube (PMT) coupled to a scintillator crystal. Which of the following option(s) is/are correct?

Your answerSelect all correct options. You can choose more than one.

A.



radiation from



will directly hit the photocathode of the PMT without interacting with the scintillator crystal and produce a signal

B.



radiation from



source interacts with the scintillator crystal, producing



radiation, which will hit the photocathode of the PMT and produce a signal

C.

A mu-metal shield is put all around the PMT to nullify the effect of external electric fields

D.

A mu-metal shield is put all around the PMT to nullify the effect of external magnetic fields

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Question 30

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PHNAT1 markNeeds review

One mole of an ideal monatomic gas at absolute temperature



undergoes free expansion to double its original volume, so that the entropy change is



. An identical amount of the same gas at absolute temperature



undergoes isothermal expansion to double its original volume, so that the entropy change is



. The value of



(in integer) is ______

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