answer all three questions

Calculate the critical angle for the light traveling from glass (nglass=1.54) to air (ndir=1.00). Express your answer in degrees. Normal format with 3 SF. QUESTION 20 An object is placed 9.0cm in front of a converging lens with a focal length of 18.8cm. Use calculation to find the location (in cm) of the image. Normal format with 3SF. QUESTION 21 In Young's double-slit interference experiment, it is found that the second bright fringe is at the angle of 11.6. If the separation between the double slits is 1.50103mm, find the wavelength (in m ) of the light source. Exponential format with 3 SF