Double-convex lenses are to be manufactured from a glass of refractive index 1.55 with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20 cm?
1. 20 cm
2. 22 cm
3. 24 cm
4. 15 cm
Monochromatic light of wavelength 589 nm is incident from the air on a water surface. What is the wavelength of reflected light? The refractive index of water is 1.33.
(1) 500 nm
(2) 545 nm
(3) 485 nm
(4) 589 nm
The refractive index of glass is 1.5. What is the speed of light in glass?
Light of wavelength 5000 Å falls on a plane reflecting surface. For what angle of incidence is the reflected ray normal to the incident ray?
A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?
(1) 1.73 cm
(2) 1.98 cm
(3) 1.01 cm
(4) 1.11 cm
A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12cm from P. At what point does the beam converge if the lens is a convex lens of focal length 20cm?
(1) 7.5 cm away from the lens on the left side.
(2) 7.5 cm away from the lens on the right side.
(3) 6.5 cm away from the lens on the left side.
(4) 6.5 cm away from the lens on the right side.
An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm. the image produced by the lens is:
(1) inverted and virtual.
(2) erect and real.
(3) erect and virtual.
(4) inverted and real.
What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm?
(1) -45 cm
(2) -55 cm
(3) -50 cm
(4) -60 cm
A compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at the least distance of distinct vision (25 cm)?
(1) 2.5 cm
(2) 0.5 cm
(3) 1.5 cm
(4) 5.0 cm
A person with a normal near point (25 cm) using a compound microscope with an objective of focal length 8.0 mm and an eyepiece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. What is the separation between the two lenses?
1. 7.20 cm
2. 9.47 cm
3. 2.50 cm
4. 2.27 cm