Optics Answers

When an object is moving along the principal axis of a lens at object distances 8 cm and 16 cm , the images being thrice the size of the object can be found. Find the type and focal length of the lens

12. An object ‘o’ , a converging lens L of focal length 15 cm where object distance is 30 cm and concave mirror M are placed. the distance between o and mirror is 50 cm. If the object and the final image coincide , the focal length of M is ( 1 ) 10 cm ( 2 ) 15 cm ( 3 ) 20 cm ( 4 ) 25 cm ( 5 ) 30 cm

Number of images formed by a pair of plane mirrors is given by n = 360/Ø, n-1 if n is even and n (asymmetrical) of n-1 (symmetrical).
What will be the number of images formed if n is a fraction example n = 360/225??

A convex (converging) lens can be used to light a fire (if you are stranded on a desert island,
for example). Consider a lens with focal length 0.200 m. How far away must a piece of
paper be held to set in on fire most effectively? Give a reason for your answer.

Consider the lens equation (1) for a convex (converging) lens. If you were to determine
where an image is formed for an object very, very far away, like the sun, an approximate
relationship between the image length and the focal point can be derived. By looking up the
distance from the earth to the sun to assist you, derive this relationship. Remember to
reference properly!

An object is moved from a distance of 30 cm to a distance of 10 cm in front of a converging lens of focal length 20 cm. What happens to the image?
(a) The image goes from real and upright to real and inverted.
(b) The image goes from virtual and upright to real and inverted.
(c) The image goes from virtual and inverted to real and upright.
(d) The image goes from real and inverted to virtual and upright.
(e) None are correct.

3. The photo detector output in a cutback attenuation set up is 3.5V at the far end of the fiber. After cutting the fiber 2m at the near end, 5km from the far end, photo detector output read was 4.2 V. What is the attenuation of fiber in dB/km?

A real image is formed with a converging lens. Which of the following actions will move the image point farther from the lens?
(a) decrease the object distance
(b) increase the radius of curvature
(c) decreases the index of refraction
(d) All are correct.

Which pair is exchanged in the reflection from a plane mirror? You may wish to draw a sketch in order to help you determine the proper answer.
(a) right and left
(b) up and down
(c) front and back
(d) None are correct.
(e) More than one of these.