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 Free problems: all problems
 Kinematics Dynamics Conservation laws Thermodynamics Waves Electricity Magnetism Optics Fluids and elasticity Ideal gas AC current

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# Physics problems:optics

image formation: thin lenses

Problem 47.

A lens is made of glass with index of refraction 1.5. One side of the lens is flat, and the other is convex with the radius of curvature of 30 cm. What is the focal length of the lens?

Solution

Problem 48.

An object is placed 40 cm in front of the lens with the focal length of 50 cm. Where is the image located? The height of the object is 1 cm. What is the height of the image?

Solution

Problem 49.

An object is placed 70 cm in front of the lens with the focal length of 50 cm. Find the position of the image. If the height of the object is 1 cm, then what is the height of the image?

Solution

Problem 50.

An object is placed 40 cm in front of the lens. The focal length of the lens is -10 cm. Find the position and the height of the image. The height of the object is 2 cm.

Problem 55.

A 1.5-cm-diameter spider is 50 cm from a wall. Determine the focal length and the position (measured from the wall) of the lens that will make a half-size image of the spider on the wall.

Solution

Problem 56.

A 2.0-cm-tall object is 3.0 m from a wall. How many places can you put the lens with the focal length of 40 cm to form a well-focused image of the object on the wall?

Solution

Problem 64.

Find the index of refraction of the glass used in a plano-concave lens of focal length -10 cm whose concave surface has a radius of 5 cm?

Solution

Problem 65.

A double-convex lens has surfaces whose radii are both 40 cm. The index of refraction of the glass of the lens is 1.6. What is the focal length of the lens?

Solution

Problem 66.

The distance between the object and the virtual image formed by a lens is 10 cm.The size of the image is 3 times the size of the object. Find the focal length of the lens and the distance between the object and the lens.

Solution

Problem 67.

The distance between the object and the virtual image formed by a lens is 20 cm. The size of the image is half the size of the object. Find the focal length of the lens and the distance between the object and the lens.

Problem 68.

The images formed by a lens is observed on a screen. The distance between the object and the image is 20 cm. The size of the image is twice the size of the object. What is the focal length of the lens? What is the distance between the object and the lens?

Problem 69.

The image formed by a lens is inverted and its size is two times the size of the object. Find the focal length of the lens and the distance between the object and the lens if the distance between the image and the object is 20 cm.

Solution

Problem 70.

The image formed by a lens is upright and two times the size of the object. The distance between the image and the object is 10 cm. Find the focal length of the lens and the distance between the object and the lens.

Solution

Problem 71.

The image formed by a lens is upright and half the size of the object. Find the focal length of the lens and the distance between the object and the lens if the distance between the image and the object is 40 cm.

Solution

Problem 72.

For a system of two lenses shown in the figure find the position of the image (distance between the image and the first lens) and the size of the image if the size of the object is 1 cm. The distance between the object and the first lens is 20 cm (see figure). The focal lengths of the first and the second lenses are 10 cm and 30 cm, respectively. The distance between the lenses is 40 cm.

Solution

Problem 73.

For a system of two converging lenses (see figure) find the position of the image (distance between the image and the second lens) and the size of the image. The distance between the object and the first lens is 10 cm (see figure). The focal length of the first lens is 20 cm and the focal length of the second lens is 40 cm. The distance between the lenses is 30 cm and the size of the object is 2 cm.

Solution

Problem 74.

Find the position of the image (distance between the image and the second lens) formed by a system of two diverging lenses shown in the figure. The focal lengths of two lens are -20 cm and -40 cm, respectively. The distance between the lenses is 20 cm and the distance between the object and the first lens is 40 cm.

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