Answer:
The diaphragm.
Explanation:
A diaphragm is a thin non transparent structure with an aperture at its center. Aperture is the opening in a lens through which light passes to enter the camera. Diaphragm controls the passage of light through specimen. It stops the passage of light except for the light passing through aperture. It also limits the brightness of light reaching the focal plane.
The diaphragm is placed close to the lens, where objects are defocused to the maximum in order to pass every ray from the object through the lens. Diaphragm discards some of those rays but allows multiple rays to move through to produce an image. This means that the size of the aperture controls the amount of light that passes through the lens. The center of the aperture coincides with optical axis of the lens. Iris diaphragm is an example. It is used in modern cameras.
Explanation:
C,
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Answer:
(1) fossel fuel
(2) Kyoto protocol
(3) all of the above
(4) Electricity usage will decrease in the near future due to shrinking world population
Forces are considered balanced when all of the combined forces lead to no change in the motion of the object. For example, when a book is sitting on a table, the force of gravity is pushing downward and the normal force is pushing upward with exactly the same amount of force. Since they are equal and opposite forces, the book does not move.
Unbalanced forces exist when there are unequal forces acting upon the object, which leads to a change in the state of motion. Unbalanced forces can lead to a change in direction, a change in speed, or both a change in direction and in speed.
Answer:
Explanation:
Given
Weight of strut 
Weight of sign Board 
In this question angle which cable makes with horizontal is not given so
assuming 
From Diagram
Moment about hinge point
in x direction is zero
in Y direction is zero therefore
