# Physical Optics-Diffraction [Optionals IAS Mains Physics]: Questions 1 - 5 of 13

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## Question 1

Diffraction
Fresnel Diffraction - Half-Period Zones and Zones Plates

Appeared in Year: 2007

### Describe in Detail

Essay▾

The radius of the first zone in a zone plate is . What will be the position of the first image of a point source of light of light of wavelength placed at a distance of from the zone plate.

### Explanation

For , the radius of the zone, the relation can be written as

is the distance of the source from the zone plate and is the distance of screen from the plate. Since (given) , the relation becomes

## Question 2

Diffraction
Fraunhofer Diffraction-Single Slit, Double Slit, Diffraction Grating, Resolving Power

Appeared in Year: 2007

### Describe in Detail

Essay▾

Define resolving power and dispersive power of a grating. Two spectral lines of wavelength and are seen clearly resolved in the second order spectral of a grating. If the grating has line per cm, what should be the minimum width of the grating?

### Explanation

• Dispersive power of a grating: It is defined as the radio of the radio of the difference in the angle of diffraction of any two neighboring spectral lines to the difference in wavelength between the two spectral lines. It can also be defined as the difference in the angle of diffraction per unit change in wavelength. The diffraction of the order p…

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## Question 3

Diffraction
Fraunhofer Diffraction-Single Slit, Double Slit, Diffraction Grating, Resolving Power
Edit

Appeared in Year: 2018

### Describe in Detail

Essay▾

2 Derive Bragg diffraction law for X-ray diffraction compare lave and Debye-Scherer methods for crystal structure determination. (Paper-2)

### Explanation

In 1912, W. H Bragg put forward a model which generates the conditions for diffraction in a very simple way. They pointed that a crystal may be divided into various sets of parallel planes. The directions of diffraction lines can then be accounted for if X- rays are considered to be reflected by such a set of parallel atomic planes followed by the …

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## Question 4

Diffraction
Fresnel Diffraction - Half-Period Zones and Zones Plates
Edit

Appeared in Year: 2017

### Describe in Detail

Essay▾

Explain with proper example the interferences to ‘division of wave front’ and ‘division of amplitude’ .

(Paper - 1)

### Explanation

The phase relation between the waves emitted by two independent light sources rapidly charges with time and therefore they can never be coherent, through the sources are identical in all respects. However, if two sources are derived from a single source by some device, then any phase change occurring in one source is simultaneously accompanied by t…

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## Question 5

Diffraction
Fraunhofer Diffraction-Single Slit, Double Slit, Diffraction Grating, Resolving Power
Edit

Appeared in Year: 2005

### Describe in Detail

Essay▾

What is the essential difference between interference and diffraction of light? How can you achieve Fraunhofer diffraction in the laboratory? Using the concept of Fraunhofer diffraction at a single slit, find out the intensity distribution produced by two slit of equal width.

### Explanation

The main differences between interference and diffraction are as follows:

 Interference Diffraction (1) Interference is the result of interaction of light coming from different wave fronts. (1) Diffraction is the result of interaction of light coming from different parts of the same wave front. (2) Interference fringes may or may not be of the same width. (2) Diffraction fringes are not of the same width.

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