Question

Find the f-number of a telescope with an objective diameter of 8.0 cm and a focal length of 95 cm.

Find the aperture diameter of an f/1.5 all-sky meteor camera lens with a focal length of 2.0 mm.

Answer #1

1)The f-number(f/stop) of an optical system is the ratio of the
system's focal length to the diameter of the entrance pupil. It is
a dimensionless number that is a quantitative measure of lens
speed. It is always represented as **f/number.**

f/number =Focal Length of the Telescope**/**
Objective(Aperture) Diameter

The answer for f/number is **f/11.875**

2) Using the same formula from above

Aperture Diameter = Focal Length of the Camera Lens / (f/number) Note- f/number is a single term

Therefore the **Aperture Diameter is 1.333
mm.**

We should know that objective diameter and the aperture diameter are the one and same things

A telescope has an objective lens with a focal length of 50 cm.
An astronomer wants his telescope to have a magnification of
(minus) 20. What should be the focal length of his eyepiece?
Can you please draw relevant diagrams and explain the working
out?
The answer should be 2.5cm.

An f/2.85 CCD camera has a 102 mm focal length lens and
can focus on objects from infinity to as near as 33.0 cm from the
lens. Note: "f/2.85" means "an f-number of
2.85."
(a)
Determine the camera's aperture diameter in mm.
mm
Determine the minimum and maximum distances in cm from the CCD
sensor over which the lens must be able to travel during
focusing.
(b)
minimum
cm
(c)
maximum
cm

An f/2.95 CCD camera has a 109 mm focal length lens and
can focus on objects from infinity to as near as 35.0 cm from the
lens. Note: "f/2.95" means "an f-number of
2.95."
HINT
(a)
Determine the camera's aperture diameter in mm.
mm
Determine the minimum and maximum distances in cm from the CCD
sensor over which the lens must be able to travel during
focusing.
(b)
minimum
cm
(c)
maximum
cm

A lens of focal length 45 mm is mounted on a 35-mm camera. The
lens aperture is set at f/2.0 and the shutter speed set at 1/2000
s. The photographer wants to keep the same exposure (amount of
light), but wants to change the f-number to f/8.0 for greater depth
of field. What should be the new shutter speed to maintain the same
exposure? Please show steps so I can understand the problem.

The focal eyepiece length of a compound microscope’s objective
lens is 0.400 cm and the focal length of the is 3.20 cm. The image
formed by the objective lens is 20.0 cm from the objective
lens.
a) Where is the object under study located? (1.5 pts)
b) If the image formed by the objective lens is located 3.00 cm
from the eyepiece, what is the distance l between the two
lenses? (1 pt)
c) Where is the final image located?...

An underwater camera has a lens of focal length 35.0 mm, a
maximum aperture of f/2.80, and the detector is sensitive to light
of wavelength 650 nm. If a diver uses the camera to photograph a
fish which is 1.5 m in front of the camera with the lens wide open,
what is the width of the smallest resolvable detail on the image of
the fish? Assume a value of 1.50 for the refractive index of
water.

The f-stop of an optical system is the ratio of the
Select one:
a. diameter of the aperture and the focal length of the
lens.
b.
focal length of the lens and the diameter of the aperture.
c. focal length of the lens and the shutter speed.
d.
diameter of the aperture and shutter speed.
e. shutter speed and diameter of the aperture.

A microscope has a 1 cm diameter objective lens with a focal
length of 2.8 mm. The microscope is using light with a wavelength
of 550 nm
a. What color is the light?
b. What is the resolving power of the objective if used in
air?
c. What is the resolving power of the objective is used in oil
with an index of refraction of 1.45?
d. Would using a longer wavelength improve the resolution? Why
or why not?

The normal lens on a 35-mm camera has a focal length of 45.0 mm
. Its aperture diameter varies from a maximum of 16 mm
(f/2.8) to a minimum of 2.0 mm (f/22).
a.) Determine the resolution limit set by diffraction for
f/2.8. Specify as the number of lines per millimeter
resolved on the film. Take ? = 560 nm.
b.) Determine the resolution limit set by diffraction
forf/22. Specify as the number of lines per millimeter
resolved on the...

The telescope at Yerkes Observatory in Wisconsin has an
objective whose focal length is 19.4 m. Its eyepiece has a focal
length of 10.0 cm. (a) What is the angular magnification of the
telescope? (b) If the telescope is used to look at a lunar crater
(diameter = 5130 m), what is the size of the first image, assuming
the surface of the moon is 3.77 × 108 m from the surface of the
earth? (c) How close does the...

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