Refraction by Spherical Surfaces: Practice Problem & Solution
The focal length of converging lens is measured for violet, green and red colours. It is respectively $f_v, f_g, f_r$. We will get (1997)
Solution Explained:
To solve this problem, we apply the core principles of Refraction by Spherical Surfaces. Understanding the underlying formula is key to arriving at the correct answer below:
According to Cauchy's relation, the refractive index is inversely proportional to wavelength, so $\mu_v > \mu_r$.[cite: 1] From the Lens Maker's formula, the focal length is inversely proportional to $(\mu - 1)$. Since violet has a higher refractive index than red, its focal length will be shorter, hence $f_v < f_r$.[cite: 1]
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