# Optionals IAS Mains Physics: Questions 125 - 132 of 307

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## Question 125

Appeared in Year: *2004*

### Describe in Detail

Essay▾A hydrogen atom is in the following state: .

What are and ?

### Explanation

As the wave function is normalized

Since

## Question 126

Appeared in Year: *2004*

### Describe in Detail

Essay▾What is the principle used in ‘half adder’ ? Give the truth table for it?

### Explanation

When we add two binary numbers, we start with the least significant column. This means that we have to add two bits with the possibility of a carry. The circuit used for this is called a half-adder. Fig (1) shows how to build a half-adder. The output of the exclusive OR gate is called the SUM, while the output of the AND gate is the CARRY. The AND …

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## Question 127

Appeared in Year: *2004*

### Describe in Detail

Essay▾Calculate the Zeeman shift observed in the normal Zeeman Effect when a spectral lime of wave length is subjected to the magnetic field of .

### Explanation

The wave number separation between the components of a normal Zeeman triplet is given by

Putting the values

Now

## Question 128

Appeared in Year: *2004*

### Describe in Detail

Essay▾Calculate the wavelength of neutrons at a temperature of .

### Explanation

Energy is given by for the neutrons.

Wave length and

## Question 129

Appeared in Year: *2016*

### Describe in Detail

Essay▾Solve the Schrodinger equation for a step potential and calculate the transmission and refection coefficient for the case when the kinetic energy of the particle is greater than the potential energy .

### Explanation

The Schrodinger equation is

Where for

For

Let us see the case when energy of the incident particle is greater than . The Schrodinger equation for region and becomes

,

,

These equations have general solution

The terms and representing the waves propagating in the – direction while the terms, and represent the…

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## Question 130

Appeared in Year: *2004*

### Describe in Detail

Essay▾Calculate the binding energy per nucleon for and .

### Explanation

The binding energy in of the nucleons which has neutrons, is given by

Where is the atomic mass of , is the neutron mass and is the atomic mass of , all in mass units. Atomic masses, not nucleon masses are used in each calculations, the election masses subtract out.

The binding energy per nucleon for a given nucleus is an average found by divi…

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## Question 131

### Explanation

Maxwell equations in differential form are: -

or

or

or

or

Taking scalar product of with and equation with .

and

Now subtracting Equation from equation , we get

Using vector identity

Now if the medium is linear so that the relations

And

We may write

Using the relationships, equation takes the form

Each term in above equation has certain physical …

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## Question 132

Appeared in Year: *2016*

### Describe in Detail

Essay▾With the help of a neat diagram, show that the potential due to a dipole at a point is given by , where is the dipole moment of the charge distribution, is the angle between the line joining the centre of the dipole to the point of interest and the axis of the dipole.

### Explanation

Let an electric dipole consist of two equal and unlike point charges at and at , separated by a small distance , with centre at . The dipole moment

Let us take the origin at the centre of the dipole. We have to calculate electric potential at any point where and angle , Fig (1)

Let the distance of from charge at be , i.e. and d…

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