PHYSICS: THIN LENS EQUATION and MAGNIFICATION PRACTICE PROBLEMS
PHYSICS
THIN LENS EQUATION AND MAGNIFICATION
PRACTICE PROBLEMS WITH ANSWERS and SOLUTIONS
Practice Problems:
1) An object 5cm high is placed 24cm away from the lens with its focal length of 8cm. Calculate
the location and height of the image formed.
2) An object is 5cm high placed 24cm away from the lens with its focal length of -8cm. Calculate
the location and height of the image formed.
3) An object is placed 6cm from the lens of f=9cm. Calculate its magnification.
4) What is the strength of diopters of a camera lens with a focal length of 50mm?
5) A zoom lens on a camera has a focal length adjustable from 80-200mm. Why are the largest and
smallest strengths of this lens in diopters?
6) Calculate the focal length of an eyeglass lens with a strength of -3.50.
7) It is possible to observe the glowing coils of a light bulb filament by projecting its image on a
screen. Suppose the light bulb filament is 15cm from a lens with a focal length of 12cm.
a) Where is the image located?
b) What is its magnification?
8) A doctor is examining a mole using a magnifying glass with a focal length of 15cm. it is held
13.5cm from the mole.
a) Calculate the position of the image formed.
b) What is the magnification of the image?
c) What is the height of the image if the mole is .50cm in diameter?
9) A magnifier is used to examine a rare butterfly held 5cm away from the lens. If the butterfly is
magnified by 3, what is the focal length of the lens?
10) A woman using a magnifying make-up mirror holds it 15cm from the face and gets a
magnification of 1.5. calculate the focal length of the mirror.
11) The eye projects a real image on the retina 2cm from its lens system. A person is looking at a
poster 2m away.
a) Calculate the focal length of the eye
b) Calculate the strength lens system of the eye in diopters
c) What is the height of the image in the retina if the poster is .75cm high?
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PHYSICS
THIN LENS EQUATION AND MAGNIFICATION
PRACTICE PROBLEMS WITH ANSWERS and SOLUTIONS
Practice Problems:
1) An object 5cm high is placed 24cm away from the lens with its focal length of 8cm. Calculate
the location and height of the image formed.
2) An object is 5cm high placed 24cm away from the lens with its focal length of -8cm. Calculate
the location and height of the image formed.
3) An object is placed 6cm from the lens of f=9cm. Calculate its magnification.
4) What is the strength of diopters of a camera lens with a focal length of 50mm?
5) A zoom lens on a camera has a focal length adjustable from 80-200mm. Why are the largest and
smallest strengths of this lens in diopters?
6) Calculate the focal length of an eyeglass lens with a strength of -3.50.
7) It is possible to observe the glowing coils of a light bulb filament by projecting its image on a
screen. Suppose the light bulb filament is 15cm from a lens with a focal length of 12cm.
a) Where is the image located?
b) What is its magnification?
8) A doctor is examining a mole using a magnifying glass with a focal length of 15cm. it is held
13.5cm from the mole.
a) Calculate the position of the image formed.
b) What is the magnification of the image?
c) What is the height of the image if the mole is .50cm in diameter?
9) A magnifier is used to examine a rare butterfly held 5cm away from the lens. If the butterfly is
magnified by 3, what is the focal length of the lens?
10) A woman using a magnifying make-up mirror holds it 15cm from the face and gets a
magnification of 1.5. calculate the focal length of the mirror.
11) The eye projects a real image on the retina 2cm from its lens system. A person is looking at a
poster 2m away.
a) Calculate the focal length of the eye
b) Calculate the strength lens system of the eye in diopters
c) What is the height of the image in the retina if the poster is .75cm high?
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