1
COMEDK 2024 Morning Shift
MCQ (Single Correct Answer)
+1
-0

The difference in energy levels of an electron at two excited levels is $$13.75 \mathrm{~eV}$$. If it makes a transition from the higher energy level to the lower energy level then what will be the wave length of the emitted radiation? [given $$h=6.6 \times 10^{-34} \mathrm{~m}^2 \mathrm{~kg} \mathrm{~s}^{-1} ; c=3 \times 10^8 \mathrm{~ms}^{-1} ; 1 \mathrm{~eV}=1.6 \times 10^{-19} \mathrm{~J}$$]

A
$$900 \mathrm{~nm}$$
B
$$9^0 \mathrm{~A}$$
C
$$9000 \mathrm{~nm}$$
D
$$900^{\circ} \mathrm{A}$$
2
COMEDK 2024 Morning Shift
MCQ (Single Correct Answer)
+1
-0

A string of length $$25 \mathrm{~cm}$$ and mass $$10^{-3} \mathrm{~kg}$$ is clamped at its ends. The tension in the string is $$2.5 \mathrm{~N}$$. The identical wave pulses are generated at one end and at regular interval of time, $$\Delta \mathrm{t}$$. The minimum value of $$\Delta \mathrm{t}$$, so that a constructive interference takes place between successive pulses is

A
0.2 s
B
1 s
C
40 ms
D
20 ms
3
COMEDK 2024 Morning Shift
MCQ (Single Correct Answer)
+1
-0

A cubical box of side $$1 \mathrm{~m}$$ contains Boron gas at a pressure of $$100 \mathrm{~Nm}^{-2}$$. During an observation time of 1 second, an atom travelling with the rms speed parallel to one of the edges of the cube, was found to make 500 hits with a particular wall, without any collision with other atoms. The total mass of gas in the box in gram is

A
30
B
0.3
C
3
D
0.03
4
COMEDK 2024 Morning Shift
MCQ (Single Correct Answer)
+1
-0

Around the central part of an air cored solenoid of length $$20 \mathrm{~cm}$$ and area of cross section $$1.4 \times 10^{-3} \mathrm{~m}^2$$ and 3000 turns, another coil of 250 turns is closely wound. A current $$2 \mathrm{~A}$$ in the solenoid is reversed in $$0.2 \mathrm{~s}$$, then the induced emf produced is

A
$$1.32 \times 10^{-1} \mathrm{~V}$$
B
$$4 \times 10^{-1} \mathrm{~V}$$
C
$$1.16 \times 10^{-1} \mathrm{~V}$$
D
$$8 \times 10^{-2} \mathrm{~V}$$
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