Question

A beam of unpolarised light of intensity
I0
is passed through a polaroid A and
then through another polaroid B which
is oriented so that its principal plane
makes an angle of 900 relative to that
of A. What is the intensity of the
emergent light when (N-1) more
polaroids are inserted between them?
Their axes are equally spaced.

Answer 1

Answer:

IαA

2

where A is the amplitude and I is the intensity

For unpolarised light, it can be resolved into two components of equal magnitude in any pair of perpendicular directions. So the amplitude that is along the plane of polarisation of the polaroid will always be

2

A

So, the intensity which will pass through it will always be

2

I

0

Now when this polarised light falls on polaroid B whose plane of polarisation makes an angle θ with the plane of polarisation of incident light, the component of amplitude along the plane of polarisation of the polaroid is Acosθ.

Therefore, intensity of light that passes through is I

i

cos

2

θ where I

i

is the intensity of incident light.

Here, I

i

=

2

I

0

and θ=45

∘

So intensity of light emerging through B is

2

I

0

×

2

1

=

4

I

0

HOPE IT HELPS

THANKS FOR YOUR QUESTION

Answer 2

Explanation:

N Ф = π/2

Ф = π /2N

Generelly

I' = I/2 cos²(Ф/2)

Here angle is cos(π/2N)²ⁿ

I' = I/2 cos(π/2N)²ⁿ