concave mirror questions parts A & B sin(30) 0.5, sin(60)-0.866 cos(30) 0.866, c

Question

concave mirror questions parts A & B sin(30) 0.5, sin(60)-0.866 cos(30) 0.866, cos(60)-0.5 9) A concave mirror has a focal length of 3 cm. a) A 1cm high object is placed 4 cm from the mirror. Using ray tracing, determine the image distance and magnification. [4 pts b) The object is replaced with a 2 cm long stick on the optical axis, with the left edge of the stick 4 cm from the mirror (the mirror is the same as in part a). How long does the stick appear to be in the image (note: the drawing below is not to scale, it's just to show you how the object is set up.)? [3 pts 2 cm 4 cm

Explanation / Answer

9) a)

the imge distance comes out to be 12 cm in front of mirror and height = 2 cm below principle axis

therefore magnification = image height / object height = 2

we can also find image distance by the formula

1/v + 1/u = 1/f

where v = image distance

u = - 4 cm is the object distance [ - sign as it is in front of mirror]

f = - 3 cm is the focal length

using the formula v =- 12 cm [ -ive shows that image formed in front of mirror]

b) using the above formula

the left edge of the object after redlection forms image at :

1/v + 1/u = 1/f

u = -4 f = -3

therefore v = -12

so image of left edge formed at 12 cm in front of mirror

the right edge of the object is formed at :

1/v + 1/u = 1/f

u = -6 f = -3

therefore v = -6

so image of right edge formed at 6 cm in front of mirror

the length of image = 12 - 6 = 6cm

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