Question

Refractive index of violet, yellow and red colour of light for a material of lens are 1.66, 1.64 & 1.62 respectively. If mean focal length of lens is 10 cm. Then chromatic aberration between the colour of violet and red will be :

• A. 0.625 cm
• B. 0.125 cm
• C. .02 cm
• D. 0 cm

Answer 1

The correct option is A 0.625 cm

Given: Refractive index of violet, yellow and red colour of light for a material of lens are 1.66, 1.64 & 1.62 respectively. If mean focal length of lens is 10 cm

To find the chromatic aberration between the colour of violet and red.

Solution:

As per the given criteria,

Refractive index of violet, ${\mu }_v=1.66$

Refractive index of yellow, ${\mu }_y=1.64$

Refractive index of red, ${\mu }_r=1.62$

If $\omega$ is the dispersive power of the material of the lens.

Average focal length, $f=10cm$

Using the relation for chromatic aberration between the colour of violet and red colors,

$=\omega \times f⟹=\frac{{\mu }_v-{\mu }_r}{{\mu }_y-1}\times f⟹=\frac{1.66-1.62}{1.64-1}\times 10⟹=\frac{0.04\times 10}{0.64}=0.625cm$

is the required chromatic aberration.