What is the shape of the wavefront of light emitted by a long neon bulb placed at a finite distance?

For a long sighted man the least distance of distinct vision is 100 cm. Calculate the power of the lens that will enable him to see an object placed at a distance of 50 cm.

A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the Sun and the Earth in terms of the new unit if light takes 8 min and 20 s to cover this distance?

What is the magnetic field at a point placed outside of a long solenoid carrying current I.

A tuning fork oscillates 350 times in second. What is the distance travelled by the sound wave emitted by the tuning fork after its 5 oscillation. The speed of sound in air is 350 m/s

An infinitely long straight current carrying wire produces a magnetic field B at a point at a distance 'a' from it. What must be the radius of the circular loop, so that for the same current through it the magnetic field at (II) an axial point, distant equal to the radius of the loop equals B?

In a potato race a bucket is placed at the starting point which is 5 m from the first potato and the other potatoes are placed 3 m apart in a straight line.There are ten potatoes in the line(see fig.below). A competitors starts from the bucket picks up the nearest potato,runs back with it,drops it in the bucket,runs back up the next potato,runs to the bucket to drop it in and she continues in the same way until all the potatoes are in the bucket.What is the distance the competitor has to run?

A LASER is a source- of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source 'of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth?