# GATE (Graduate Aptitude Test in Engineering) Physics: Questions 628 - 632 of 659

Access detailed explanations (illustrated with images and videos) to **659** questions. Access all new questions- tracking exam pattern and syllabus. View the complete topic-wise distribution of questions. *Unlimited Access, Unlimited Time, on Unlimited Devices*!

View Sample Explanation or View Features.

Rs. 450.00 -OR-

How to register? Already Subscribed?

## Question 628

Appeared in Year: *2017*

### Describe in Detail

Essay▾The atomic mass and mass density of Sodium are and , respectively. The number density of valence electron is . (Up to two decimal places) (Avogadro number, )

### Explanation

The number density of valence electrons is,

Where, is the valency.

is the mass density

is the atomic mass

is Avogadro number.

According to question, for sodium;

## Question 629

Appeared in Year: *2017*

### Question

MCQ▾The real space primitive lattice vectors are and . The reciprocal space unit vectors and for this lattice are, respectively;

### Choices

Choice (4) | Response | |
---|---|---|

a. | and | |

b. | and | |

c. | and | |

d. | and |

## Question 630

Appeared in Year: *2017*

### Describe in Detail

Essay▾The total energy of an inert – gas crystal is given by , where is the inter – atomic spacing in Angstroms. The equilibrium separation between the atoms is ________ Angstroms. (up to two decimal places) .

### Explanation

Here, the total energy of an inert – gas crystal is given,

Where, is the inter – atomic spacing in Angstroms.

If at equilibrium, separation between atoms is , then becomes minimum. Therefore,

… (2 more words) …

## Question 631

Appeared in Year: *2017*

### Describe in Detail

Essay▾Consider a 2 – dimensional electron gas with a density of . The Fermi energy of the system is (up to two decimal places) .

### Explanation

The Fermi – energy of 2 – dimensional electron gas with a density of is given as,

… (2 more words) …

## Question 632

Appeared in Year: *2017*

### Question

MCQ▾If the Lagrangian is modified to , which one of the following is TRUE?

### Choices

Choice (4) | Response | |
---|---|---|

a. | The canonical momentum and equation of motion do not change | |

b. | Canonical momentum does not change, equation of motion changes | |

c. | Canonical momentum changes, equation of motion does not change | |

d. | The canonical momentum and equation of motion change |