The next part of this exercise examines further the concept of focal length. A)
ID: 2155596 • Letter: T
Question
The next part of this exercise examines further the concept of focal length.
A)
The lens in the last part is used to form the image of the sun. What is the image distance? (Recall that the focal length is 7 cm.)
B)
An object is located at the focal point of the lens. The image of the object is located at. (This part is asking for a word, not a number.)
PLEASE HELP!! Having trouble with this part.
When parallel rays pass through a converging lens, the rays converge at a point called the focal point. The distance between the lens and the focal point is the focal length. This length is a characteristic of the lens and is determined from the radius of curvatures and the refractive index of the lens. In the Figure below a lens of focal length 7 cm is placed between a plane mirror and a pin hole. The other side of the pin hole is illuminated by a light source (not shown), so that the light passes through the hole and is then collected by the lens.If the pin hole is at the focal point of the lens, then the light that passes through the lens will be parallel.When the parallel rays hit the plane mirror, the reflected rays will also be parallel, and when they pass through the lens again the rays will be focused at the pin hole. This is called the auto-collimation method for finding the focal length of a lens. For this part, the object is to find the location to place the lens and the pin hole to obtain auto-collimation. The next part of this exercise examines further the concept of focal length. A) The lens in the last part is used to form the image of the sun. What is the image distance? (Recall that the focal length is 7 cm.) B)An object is located at the focal point of the lens. The image of the object is located at. (This part is asking for a word, not a number.)Explanation / Answer
a) As the sun distance is so great we take it as 1/object distance = 0
so, 1/image distance = 1/focal length
image distance = focal length
image distance = 7 cm
b) When the object is located at the focal point, the image will be located at infinity or we can say because the rays from the object at the focal point emerge from the lens parallel to the optical axis, all the way to infinity. Because the rays never come together on that side of the lens, no image is formed.
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