Exam 33: Lenses and Optical Instruments

A diverging lens is fabricated from a piece of glass with an index of refraction of 1.5.It is ground such that one surface of the lens is convex and the other surface is concave.The convex surface is part of a sphere with a radius of 45 cm and the concave surface is part of a sphere with a radius of 20 cm.What is the power of this lens in diopters?

A physics student epoxies two converging lenses to the opposite ends of a 20-cm long tube.One lens has a focal length of f₁ = 4.0 cm and the other has a focal length of f₂ = 2.0 cm.She wants to use this device as a microscope.What is the magnification of this homemade microscope?

A thin spherical lens is fabricated from glass with an index of refraction of 1.5.The lens is fabricated so that it bulges outwards in the middle on both sides,and has been ground so that the surfaces are part of a sphere with a radius of 20 cm on one side and a radius of 50 cm on the other.What is the power of this lens in diopters?

Suppose a reflecting telescope consists of a convex spherical mirror with a radius of curvature R =15.0 m and an eyepiece lens of focal length fe = 30.0 cm.What is the magnitude of the magnification of this telescope?

A bracken fern spore produces an image that is 7.5 cm tall when placed before a converging lens of focal length 5.0 cm.If the spore's true height is 1.5 mm,how far from the lens was it placed?

The greatest distance a person can see an object in focus is 35.0 cm in front of his eyes.What power of eyeglasses should he wear in order to see distant objects clearly? His eyeglasses sit 2.0 cm in front of his eyes.

A person wears bifocal glasses and is reading a newspaper a distance of 20.0 cm away.The lower part of the lens is converging for reading and has a focal length of 70.0 cm.The upper part of the lens is diverging for seeing at distances far away and has a focal length of 50.0 cm.What is the uncorrected far point for the person?

A system of two converging lenses 7.5 cm apart from each other is used to examine a leaf from a distance (to the first lens)of 25 cm.If the focal lengths of the two lenses are 12 cm and 17 cm,respectively,what is the magnification of the image?

A real image is formed with a converging lens.Which of the following actions will move the image point farther from the lens?

A diver with 20/20 vision removes his mask underwater.What can be said about how the diver sees without his mask underwater? The index of refraction of water is 1.3 and the index of refraction for a human lens is 1.4.

Two lenses are used to create an image of a 15.0-cm tall source that is located 43.0 cm to the left of the first lens,which is a biconcave thin polycarbonate lens (index of refraction n = 1.67)and has a radius of curvature of 25.0 cm for both front and back surfaces.The second lens is 36.0 cm to the right of the first lens.The second lens is a converging lens with a focal length magnitude of 25.0 cm.At what position relative to the object does the image get formed?

A lens with an unknown focal length forms an image of an object that is 12 cm away from the lens,inverted,and a factor of 3.0 larger in size than the object.Where is the object located?

A physics student epoxies two converging lenses to the opposite ends of a 20-cm long tube.One lens has a focal length of f₁ = 4.0 cm.She wants to use this device as a microscope.If the desired magnification of this homemade microscope is 80,what focal length should the student use for the the second lens?

A convex lens with index of refraction n = 1.60 has two spherical surfaces as shown in the diagram.The radius of curvature of the left face is r1 = 1.50 m.The radius of curvature of the right face is r2 = 1.70 m.What is the focal length (in m)of this lens?

The objective lens in a laboratory microscope has a focal length 4.00 cm and provides an overall magnification of 250.What is the focal length of the eyepiece if the distance between the two lenses is 32.0 cm?

The focal length of the lens of a camera is 38.0 mm.How far must the lens be moved to change focus from a person 50.0 m away to one that is 5.0 m away?

Laser-Assisted in Situ Keratomileusis (LASIK)surgery uses a laser to modify the

Three converging lenses of focal length 5 cm are arranged with a spacing of 20 cm between them,and are used to image an insect 20 cm away from the first lens.Where is the image with respect to the third lens?

A person wears bifocal glasses and is reading a newspaper a distance of 20.0 cm away.The lower part of the lens is converging for reading and has a focal length of 70.0 cm.The upper part of the lens is diverging for seeing at distances far away and has a focal length of 50.0 cm.What is the uncorrected near point for the person?

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?