Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11
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# Suppose, the Electron in a Hydrogen Atom Makes Transition from N = 3 to N = 2 in 10−8 S. the Order of the Torque Acting on the Electron in this Period, Using the Relation Between - Chemistry

MCQ
Sum

Suppose, the electron in a hydrogen atom makes transition from n = 3 to n = 2 in 10−8 s. The order of the torque acting on the electron in this period, using the relation between torque and angular momentum as discussed in the chapter on rotational mechanics is

#### Options

• 10−34 N m

• 10−24 N m

• 10−42 N m

• 10−8 N m

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#### Solution

10−42 N-m

The angular momentum of the electron for the nth state is given by

L_n = (nh)/(2pi)

Angular momentum of the electron for n = 3,
n = 3 , L_i = (3h)/(2pi)

Angular momentum of the electron for n = 2, L_f= (2h)/(2pi)

The torque is the time rate of change of the angular momentum.

Torque tau = (L_f - L_i)/t

= ((2h//2pi)-(3h//2pi))/10^-8

= -(h//2pi)/((10^-8)

= (-10^-34)/10^-8   ..............[∴ h/(2pi) ≈ 10^-34 J -s ]

= -10-42 N - m

The magnitude of the torque is 10^-42 N.m

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#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 21 Bohr’s Model and Physics of Atom
MCQ | Q 3 | Page 383
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