White light illuminates a 2-cm wide diffraction grating at normal incidence. The

Question

White light illuminates a 2-cm wide diffraction grating at normal incidence. The dispersed light falls upon a viewing screen. The entire first-order and second-order patterns are observed. The four arrows in the figure below represent the first- and second-order red and blue bands. Let the wavelengths of red and blue light be 700 nm and 400 nm, respectively. Identify the color of each of the four bands by entering the wavelength of the light in the appropriate box. 2 grating 0o incident light 1) The wavelength of band 1 is nm Submit 2) The wavelength of band 2 is Submit

Explanation / Answer

1) 400

2) 700

3) 400

4) 700

5) Use: d sin (th) = m lambda

=> d = (m) lambda/sin(th)

= (4)(700*10^-9)/sin(60)

= 3.233 x 10^-6

This is for For both sides of the center, so actually

d= (3.233 x 10^-6)/2 = 1.6165 x 10^-6 m = 1.6165 x 10^-4 cm

Thus,

number of lines = 1/d = 6186 lines/cm

6) No

7) Yes

8) Yes

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