*Question*

The diagram shows the diffraction pattern for light passing through a single slit.

What is \(\frac{\text{wavelength of light}}{\text{width of slit}}\)

A 0.01

B. 0.02

C 1

D 2

**▶️Answer/Explanation**

Ans: A

- The width of the central maxima is and angular width of central maxima is.

Hence \(\frac{\lambda}{b}=\) diffraction angle \(\theta\)

Hence as per given value in graph

\(\frac{\lambda}{b}= 10^{-2} = 0.001\)

*Question*

A beam of monochromatic light is incident on a single slit and a diffraction pattern forms on the screen.

What change will increase *θ*_{s}?

A. Increase the width of the slit

B. Decrease the width of the slit

C. Increase the distance between the slit and the screen

D. Decrease the distance between the slit and the screen

**▶️Answer/Explanation**

### Markscheme

B

**FRAUNHOFER DIFFRACTION BY SINGLE SLIT**

\(\therefore b \downarrow \Rightarrow sin\theta \uparrow\)

*Question*

A single-slit diffraction experiment is performed using light of different colours. The width of the central peak in the diffraction pattern is measured for each colour. What is the order of the colours that corresponds to increasing widths of the central peak?

A. red, green, blue

B. red, blue, green

C. blue, green, red

D. green, blue, red

**▶️Answer/Explanation**

### Markscheme

C

- The width of the central maxima is and angular width of central maxima is.

Hence width of the central maxima increases with increase in wavelength.

We can see lowest wavelength is blue and highest for red for blue, green, red

*Question*

A parallel beam of coherent light of wavelength *λ* is incident on a rectangular slit of width *d*. After passing through the slit the light is incident on a screen a distance *D* from the slit where* D* is much greater than *d*. What is the width of the central maximum of the diffraction pattern as measured on the screen?

A. \(\frac{{2D\lambda }}{d}\)

B. \(\frac{{2d}}{{D\lambda }}\)

C. \(\frac{{D\lambda }}{d}\)

D. \(\frac{d}{{D\lambda }}\)

**▶️Answer/Explanation**

### Markscheme

A

- The
**width of the central maxima is**and angular width of central maxima is.

### Question

The intensity distribution of monochromatic light passing through a narrow slit and then incident on a screen is shown below.

When the slit width is reduced which diagram shows the new intensity distribution? Diagrams are drawn to the same scale as the original.

**▶️Answer/Explanation**

## Markscheme

B

The width of the central maxima is .

When b is reduced width of the central maxima is is increased .