Chapter 24, Problem 6Q

To determine

To Explain: The change in fringe pattern if red light is replaced by blue light.

Answer to Problem 6Q

The bright spots on screen are tightly packed together with the blue light as compared with red light.

Explanation of Solution

Introduction:Young’s double-slit helps to understand the wave theory of light. For this it uses two coherent sources of the light.

It is known that $d\sin \left(\theta \right)=m\lambda$ Where, $m$ is an integer, $\lambda$ is wavelength and $d$ is a distance. When the red light is changed to blue light, wavelength of light will be smaller.

So, according to $d\sin \left(\theta \right)=m\lambda$ , $\theta$ will be decrease for a particular $m$ and d. Thus, bright spots on screen will be more tightly packed together with the blue light as compared to red light.

Conclusion: Hence, for blue light, the bright spots will appear closer together.