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(B) The lens maker's formula is given by: $\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.According to Cauchy's equation,the re

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increase

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(B) The lens maker's formula is given by: $\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.According to Cauchy's equation,the refractive index $\mu$ is inversely proportional to the square of the wavelength $\lambda$ (approximately $\mu \propto \frac{1}{\lambda}$). Since the wavelength of red light $(\lambda_r)$ is greater than the wavelength of blue light $(\lambda_b)$,the refractive index for red light $(\mu_r)$ is less than the refractive index for blue light $(\mu_b)$.From the formula,$f \propto \frac{1}{(\mu - 1)}$. Since $\mu_r Therefore,the focal length for red light $(f_r)$ will be greater than the focal length for blue light $(f_b)$.Thus,the focal length increases.

When monochromatic red light is used instead of blue light in a convex lens,its focal length will .....

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