Question

1. green light is shone onto two soap films, an observer looking down at the soap films sees that soap film X appears uniformly green while soap film Y has green and black bands - if the air is the medium on either side of the soap film, the best explanation of this pattern is that:

a) Film X has a thickness much less than lamda (wavelength) and film Y has a thickness of 1/4lamda.

b) Film X has a thickness of 1/2lamda and film Y has a thickness of 1/4lamda.

c) Film X has a thickness of 1/4lamda and film Y has a thickness of 1/2lamda.

d) film X has consistent thickness throughout whereas film Y has variable thickness.

e) film X has variable thickness whereas film Y has consistent thickness

2. As a student is performing a double slit experiment to determine the wavelength of a light source, she realizes that the nodal lines are too close together to be accurately measured. To increase the distance between the nodal lines she could:

a) decrease the slit seperate on

b) move the light closer to the slits

c) decrease the distance between the slits and the screen

d) both a and c

e) a, b and c

3. Astudent is performing a double slit experiment to determine the wavelength of a light source. She has measured the distance between dark bands and the distance between the slits and the screen, she still needs to measure:

a) the speed of light

b) the width of each slit

c) the distance between the slits

d) the angle between the right bisector and the first minima

e) the distance between the centre of the slits and the first minima

Answer 1

Answer:-1) the equation of path difference is 2ut=n(lambda)

Then, if medium is air so u=1 which means for alternate Bright and dark band must have thickness of lambda /2.

So, then option (c) is correct.

Answer(2)

d sin(theta)=n(lambda)

Then sin(theta ) is larger when d will be less and d is the distance between two slits.

Option(a) is correct.

Answer(3):-

For wavelength , d (y/D)=[(2n-1)/2]lambda

She has noticed all the things but for wavelength she musth note the distance between centre and first minima (y).

Then option(e) is correct.