Question

calculate object and image distance of concave mirror produces magnification of 0.65 and focal length of 10 cm

Answer 1

Questions: 5, 12, 13, 14
Exercises & Problems: 1, 12, 19, 32, 36, 37, 71, 72
Q18.5: If you take a walk on a summer night along a dark, unpaved road in the woods,
with a flashlight pointing at the ground several yards ahead to guide your steps, any
water-filled potholes are noticeable because they appear much darker than the
surrounding dry road. Explain why.
Q18.5. Reason: The water-filled potholes appear darker because the light from your
flashlight reflects off the smooth water surface into the forward direction rather than
reflecting from a rough surface in fairly random directions—some of which would be
back to your eye—as is the case on the rest of the dirt road.
Assess: If someone else were approaching you on the dirt road they could see the water
puddles as bright if the angle of reflection from your flashlight beam is such as to get the
light into their eyes.
Q18.12: A concave mirror brings the sun’s rays to a focus at a distance of 30 cm from the
mirror. If the mirror were submerged in a swimming pool, would the sun’s rays be
focused nearer to, farther from, or at the same distance from the mirror?
Q18.12. Reason: While the law of refraction depends on the index of the media, the
law of reflection does not. Under water the angle of incidence will still be equal to the
angle of reflection. There is no reason for a ray to travel a different path in water than in
air in this case. Hence, the sun’s rays will be focused the same distance from the mirror.
Assess: Of course the preceding analysis is not true for light passing through a lens that
might be immersed in either water or air; in that case the index of refraction matters. But
with a mirror the water doesn’t change anything.
Q18.13: A student draws a ray diagram but forgets to
label the object, the image, or the type of lens used. Using
the diagram, explain whether the lens is converging or
diverging, which arrow represents the object, and which
represents the image.
Q18.13. Reason: The lower ray is the ray through the center of the lens and does not
bend; consequently, it could have come from either arrow, so it doesn’t help us determine
which arrow is the object and which is the image.
Therefore the upper ray must be the key. If the larger arrow on the left were the object
then that upper ray should refract at the lens and go in a different direction, but the
diagram doesn’t show this.
The only other option is that the smaller arrow on the right is the object. We see the ray