Exam 27: Optical Instruments

Without glasses,a person can comfortably read a magazine when it is held at 60 cm from his eyes.What should be the focal length of his contact lenses to allow him to read the magazine comfortably at a distance of 30 cm?

Jack and Mary view the same microorganism through the same compound microscope.Mary's near point distance,N_M,is twice as large as Jack's near point distance,N_J.If Mary sees the microorganism with magnification M_M,with what magnification does Jack see it?

Diego is nearsighted and cannot see things beyond 110 cm from his eyes.What is the focal length of the contact lenses that will enable him to comfortably see distant hills clearly?

What type of lens is used to make a magnifying glass?

A little known fact is that both Robinson Crusoe and Friday wore eyeglasses.As it so happens,Robinson Crusoe was farsighted while Friday was nearsighted.Whose eyeglasses did they use whenever they wanted to start a fire by focusing the sun's rays?

What is the focal length of the corrective contact lens needed by a nearsighted person whose far point is at 60 cm?

The angular magnification of a refracting telescope is 40.When the object and final image are both at infinity,the distance between the eyepiece and the objective is 143.5 cm.The telescope is used to view a distant radio tower.The real image of the tower,formed by the objective,is 6.0 mm in height.The focal point of the eyepiece is positioned at the real image.What is the angle subtended by the final image of the tower?

The distance between the object to be viewed and the eyepiece of a compound microscope is 25.0 cm.The focal length of its objective lens is 0.200 cm and the eyepiece has a focal length of 2.60 cm.What is the magnitude of the total magnification of the microscope when used by the person of normal eyesight if it is designed for minimum eyestrain?

The closest object that a typical young person with normal vision can focus on clearly is closest to

Which one of the following is normally not a characteristic of a simple two-lens refracting astronomical telescope?

The focal lengths of the objective lens and the eyepiece in a microscope are 2.90 mm and 2.50 cm,respectively.An object is placed 3.00 mm from the objective.The image of this object is viewed with the eyepiece adjusted for minimum eyestrain for persons with a near point of 25 cm.What is the distance between the objective and the eyepiece?

An astronomical refracting telescope is made from two lenses.The objective lens has a focal length of And the eyepiece lens has a focal length of (a)What is the total length of the telescope? (b)What is the angular magnification of the telescope? (c)What is the magnification by turning the telescope around and looking through the objective lens first?

Which one of the following is a characteristic of a compound microscope?

What power contact lens is needed to correct for farsightedness where the uncorrected near point is 75 cm?

The focal length of the lens of a simple film camera is 40.0 mm.By what amount should the distance between the lens and the film be increased or decreased to change the focus from a person who is 25 m from the lens to one who is 4.0 m from the lens?

A person's near point is 25 cm,and her eye lens is 2.7 cm away from the retina.What must be the focal length of this lens for an object at the near point of the eye to focus on the retina?

The focal lengths of the objective lens and the eyepiece of a microscope are 0.50 cm and 2.0 cm,respectively,and their separation is 6.0 cm when adjusted for minimum eyestrain for a person with a near point of 25.0 cm.If the microscope is focused on a small object,the magnitude of its final overall magnification is closest to

The objective lens and the eyepiece of a microscope have focal lengths of 4.0 mm and 25 mm,respectively.The objective produces a real image 30 times the size of the object,with the final image viewed at infinity.The near point of the microscope user is at 25 cm.What is the magnitude of the overall magnification of the microscope?

The angular magnification of a refracting telescope is 40.When the object and final image are both at infinity,the distance between the eyepiece and the objective is 143.5 cm.The telescope is used to view a distant radio tower.The real image of the tower,formed by the objective,is 6.0 mm in height.The focal point of the eyepiece is positioned at the real image.What is the focal length of the objective lens?

When a person with a near point at 28 cm uses a certain magnifying glass,it produces an angular magnification of 7.0 with the image very distant.What is the focal length of the lens of this magnifying glass?