<h3>Concave or diverging lens is needed correct the vision of a nearsighted person whose far point is 30.0 cm</h3>
<em><u>Solution:</u></em>
Nearsighted person will not be able to see the distant objects clearly
Now, we want the near sighted person to see the distant objects clearly
<em><u>The lens equation is given as:</u></em>

For distant vision, 

The image of 30 cm from eye will be 28.5 cm to left of spectacle lens
Therefore,

From lens equation,

The negative power -3.51 D denotes that a concave or diverging lens is needed
Mechanical advantage is defined as the ratio of output load to the input load. The mechanical advantage of the machine will be 0.1.
<h3>What is
mechanical advantage?</h3>
Mechanical advantage is a measure of the ratio of output force to input force in a system,
It is used to obtain the efficiency of forces in levers and pulleys. It is an effective way of amplifying the force in simple machines like levers.
The theoretical mechanical advantage is defined as the ratio of the force responsible for the useful work in the system to the applied force.
Given
applied force = 250 N
Output force = 25
Mechanical advantage = work output / work input



Hence the mechanical advantage of the machine will be 0.1
To learn more about the mechanical advantage refer to the link;
brainly.com/question/7638820
Answer:
Explanation:
When a camera shifts focus from a faraway object to a nearby object, the lens-to-film distance must increase. Likewise, when it shifts focus from a nearby object to a distant object, there must be an increase in the lens to film distance (that is, the image distance).
Therefore, if the picture of an object that is far away, the lens must move towards the film.
The focal length cannot be changed because it is fixed for a lens. Nevertheless, in order to focus on an object, the image distance can be changed.
That's wave 'diffraction'.
Answer:
(a) 1.414 km
(b) 1.06 m/s
Explanation:
(a) For John:
Distance = 1 km north and then 1 km east
Speed = 1.5 m/s
total distance traveled = 1 + 1 = 2 km = 2000 m
Time taken to travel = Distance / speed
t = 2000 / 1.5 = 1333.3 seconds
Displacement =
(b) For jane :
Time is same as john = 1333.33 second
Distance = 1.414 km = 1414 m
Speed = distance / time = 1414 / 1333.33 = 1.06 m/s