To solve this problem it is necessary to apply the concepts related to the condition of path difference for destructive interference between the two reflected waves from the top and bottom of a surface.

Mathematically this expression can be described under the equation

$\delta = 2nt$

Where

n = Refractive index

t = Thickness

In terms of the wavelength the path difference of the reflected waves can be described as

$\delta = \frac{\lambda}{4}$

Where

\lambda = Wavelenght

Equation the two equations we have that

$2nt = \frac{\lambda}{4}$

$t = \frac{\lambda}{8n}$

Our values are given as

$\lambda = 380nm \rightarrow$ Wavelength of light

$n = 1.4$

$t = \frac{380nm}{8*1.4}$

$t = 33.93nm$

Therefore the minimum thickness of the oil for destructive interference to occur is approximately 34.0 nm

4 0

3 years ago

If a book is knocked off a desk that is .75 m tall at a rate of 2.0 m/s, how far away from the desk does it fall

ANEK [815]

Answer: 0.8 m

Explanation:

In the vertical direction, the speed is zero, u = 0.

Distance covered in the vertical direction, s = 0.75 m.

The book would fall with acceleration due to gravity in the vertical direction, a = g = 9.8 m/s²

From the equation of motion,

s = u t + 0.5 a t²

Substituting the above values, we will find out the time taken for the book to hit the ground.

⇒0.75 m=0+0.5×9.8 m/s²×t²

⇒t = √0.153 = 0.39 s ≈ 0.40 s

Now, the horizontal distance covered,

d = v×t ⇒d= 2.0 m/s × 0.40 s =0.8 m

Hence, the book falls 0.8 m away from the desk.

7 0

3 years ago