A 5.0 cm real object is placed at a distance of 5.0 cm from a concave mirror of focal length 10 cm. Find the size of the image.
A. 5 cm
B. 10 cm
C. 17 cm
D. 20 cm
I think it is B?
A(n) _______ lens is used to produce a real image.
A. convex
B. concave
C. plane
D. diverging
Is it b?
correct, incorrect
it isn't C or D, it's A..
To find the size of the image in the first question, we can use the mirror formula:
1/f = 1/v - 1/u
Where:
- f is the focal length of the concave mirror
- v is the image distance (distance of the image from the mirror)
- u is the object distance (distance of the object from the mirror)
Given:
- f = 10 cm (focal length)
- u = 5 cm (object distance)
By substituting these values into the mirror formula, we can solve for v:
1/10 = 1/v - 1/5
Multiplying through by 10v:
v = v/10 - 2
Multiplying by 10:
10v = v - 20
Combining like terms:
9v = -20
Dividing both sides by 9:
v ≈ -2.22 cm
The negative sign indicates that the image is virtual (not real) and upright (not inverted). Since the image is virtual, we cannot determine its size. Therefore, none of the given options (A, B, C, D) is the correct answer.
As for the second question, a real image is produced by a convex lens, not a concave lens. Therefore, the correct answer is A. convex.