Question

Two microscope slides made of glass are illuminated by monochromatic (λ=589nm) light incident perpendicularly. The top slide touches the bottom slide at one end and rests on a thin copper wire at the other end, forming a wedge of air. The diameter of the copper wire is 29.45μm. How many bright fringes are seen across these slides?

Answer 1

Approximately 100 bright fringes are seen across the microscope slides when illuminated by 589 nm monochromatic light due to the constructive interference of light with a wedge of air formed by a 29.45 μm diameter copper wire.

Step-by-step explanation:

Calculating the Number of Bright Fringes

Firstly, we know that the light forms a pattern of bright and dark fringes called interference fringes due to the varying air wedge thickness created between the two glass slides. The pattern is a result of the constructive and destructive interference of the monochromatic light of wavelength λ = 589 nm when reflected from the top and bottom surfaces of the air wedge.

The number of bright fringes formed can be determined by finding the number changes from constructive to destructive interference across the slides. For a wedge-shaped air gap, one complete cycle from a bright fringe to the next bright fringe occurs when the air gap changes by λ/2. The number of fringes (N) can be calculated using the equation:

1. 
   
3. 
   
5. 
   

After performing these steps, we get:

N = 99.8 ≈ 100 bright fringes.

Therefore, approximately 100 bright fringes are seen across the slides.