Posted by **Jim** on Saturday, March 31, 2012 at 4:11pm.

Light waves with two different wavelengths, 632 nm and 474 nm, pass simultaneously through a single slit whose width is 7.63 x 10-5 m and strike a screen 1.30 m from the slit. Two diffraction patterns are formed on the screen. What is the distance (in cm) between the common center of the diffraction patterns and the first occurrence of the spot where a dark fringe from one pattern falls on top of a dark fringe from the other pattern?

- Physics -
**drwls**, Saturday, March 31, 2012 at 5:37pm
The condition for an intensity minimum is b sin á = k ë

where b is the slit width.

For 474 nm, there are minima at

sin á = 6.21*10^-3 (k=1)

1.242*10^-3 (k=2)

1.864*10^-2 (k=3)

2.484*10^-2 (k=4)

For 632 nm, there are minima at:

sin á = 8.283*10^-3 (k=1)

1.657*10^-3 (k=2)

2.485*10^-2 (k=3)

Clearly, the k=4 minimum of ë = 474 nm radiation coincides with the k = 3 minimum of 632 nm radiation. The distance from the central maximum is

d = 1.30 m*sin á = 3.23*10^-2 m

= 3.23 cm

- Physics -
**drwls**, Saturday, March 31, 2012 at 5:55pm
For further reading, try

http://www.walter-fendt.de/ph14e/singleslit.htm

The a' symbol in my answer above was meant to be the diffraction angle alpha, and the e with two dots was supposed to be the wavelength, lambda

- Physics -
**Elena**, Saturday, March 31, 2012 at 6:06pm
Let’s use the condition of diffraction minimum for one split of the width b

b•sinα =k1•λ1

b•sinα =k2•λ2,

Since we have superposition of two maxima b•sinα is the same for two wavelengths,

k1•λ1= k2•λ2,

λ1/λ2 = k2/k1,

632/474 = 4/3.

Therefore, k1=3, k2=4.

Now sinα = k1•λ1/b =3•632•10^-9/ 7.63•10^-5 =0.0248.

As the angle is very small tanα = sinα,

x=L• tanα =L• sinα =1.3•0.0248 =0.0323 m = 3.23 cm

## Answer this Question

## Related Questions

- Physics - Light waves with two different wavelengths, 632 nm and 474 nm, pass ...
- Physics help please! - Light waves with two different wavelengths, 632 nm and ...
- physics - A flat screen is located 0.43 m away from a single slit. Light with a ...
- physics - single-slit diffraction pattern is formed when light of 680.0 nm is ...
- Physics - In a single-slit diffraction pattern on a flat screen, the central ...
- Physics 2 - Light with λ = 530 nm passes through a single slit and then ...
- Physics - Light of a red laser (wavelength λ=650 nm) goes through a narrow ...
- Physics ~ important due tomorrow! - A student sets up a laser and screen and a ...
- physics - In a double-slit experiment, two beams of coherent light traveling ...
- Physics - A light beam ( 557.1 nm) illustrates a single slit 0.85mm wide. (a) ...

More Related Questions