Question

$\underline{\:\large{\textit{Q\sf uestion :}}}$

In Young’s experiment, the distance between slits is 0.28 mm and distance between slits and screen is 1.4 m. Distance between central bright fringe and third bright fringe is 0.9 cm. What is the wavelength of used light​

Answer 1

★Solution :-

As per the given data ,

• Distance between the two slits (d)= 0.28 mm = 0.28 x 10⁻³ m= 28 x 10⁻⁵

• Distance between the slit and the screen(D) = 1.4 m

• Distance between the central bright fringe and the third bright fringe(y) = 0.9 x 10⁻² m =9x10⁻³

Bright fringes are formed due to the constructive interference of light

The formula used to find constructive interference between two bright fringes is

$\longrightarrow\mathtt{y =\dfrac{ n \lambda D }{d}}$

On rearranging ,

$\longrightarrow\mathtt{ \lambda=\dfrac{ yd }{nD}}$

Now let's substitute the given values in the above equation ,

$\longrightarrow\mathtt{ \lambda=\dfrac{ 9 \times 10^{-3} \times 28 \times 10^{-5} }{3 \times 1.4 }}$

$\longrightarrow\mathtt{ \lambda=\dfrac{ 252\times 10^{-8}}{4.2 }}$

$\longrightarrow\mathtt{ \lambda=60 \times 10^{-8} m}$

The wavelength of the light is 60 x 10^-8 m

Answer 2

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