10.4 In a Young’s double-slit experiment, the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in the experiment.

10.5 In Young’s double-slit experiment using monochromatic light of wavelength l, the intensity of light at a point on the screen where path difference is l, is K units. What is the intensity of light at a point where path difference is l/3?

9.26 Assume microscope in normal use i.e., image at 25 cm. Angular magnification of the eye-piece 25 =  1  6 5 Magnification of the objective 30 =  5 6 1 1 1 − = 5u O u O 1.25 which gives uO= –1.5 cm; v0= 7.5 cm. |ue| (25/6) cm = 4.17 cm. The separation between the objective and the eye-piece should be (7.5 + 4.17) cm = 11.67 cm. Further the object should be placed 1.5 cm from the objective to obtain the desired magnification.