Question 220: Wave Optics

Question

White light is passed through a double slit and interference is observed on a screen 1.5 m away. The separation between the slits is 0.3 mm. The first violet and red fringes are formed 2.0 mm and 3.5 mm away from the central white fringes. the difference in wavelengths of red and violet light is ................ nm.

Accepted Answer

Position of bright fringe y = n$${{D\lambda } \over d}$$
y
1
of red = $${{D{\lambda _r}} \over d}$$ = 3.5 mm
$$\lambda$$
r
= 3.5 $$	imes$$ 10
$$-$$3
$${d \over D}$$
Similarly, $$\lambda$$
v
= 2 $$	imes$$ 10
$$-$$3
$${d \over D}$$
$${\lambda _r} - {\lambda _v} = (1.5 	imes {10^{ - 3}})\left( {{{0.3 	imes {{10}^{ - 3}}} \over {1.5}}} ight)$$
= 3 $$	imes$$ 10
$$-$$7
= 300 nm

Wave Optics

Integer / Numeric Answer Type