Question

please help, thank you

The electric field in an EM wave is given by (In SI units): Ē = $(15) sin(1.1x10' x-0) [N/C] where ſ is the unit vector in the y-axis. calculate its wavelength. The pilot of an aircraft flying over a lake notices an illuminated circular path of diameter 20.0 m at the surface of the water due to a very bright light source at the bottom of the lake. Assuming that the light source emits equally in all directions and no light is reflected from the side of the lake, calculate the depth of water in the lake. The index of refraction of the water is 1.40. An object is placed 26.0 cm in front of convex lens of focal length 40.0 cm. What is the magnification of the image?

Answer 1

1) k = 1.1*10^7 and k = 2*3.14/wavelength

w = 6.28/1.1*10^7

w = 5.71*10^-7

w = 571 nm

2) we can solve it by equation,

Radius = depth*tan(critical angle)

C = 45.58 degree

10 = depth*tan(45.58)

depth = 10/1.0204

depth = 9.8 m

3) using lens formula,

1/f = 1/v - 1/u

1/v = 1/40 - 1/26

v = - 74.28 cm

Magnification : m = v/u

m = 74.28/26

m = 2.85