7. 5
List the sign conventions that are followed in case of refraction of
light through spherical lenses. Draw a diagram and apply these
conventions in determining the nature and focal length of a
spherical lens which forms three times magnified real image of an
object placed 16 cm from the lens.​

f=ma newton's second law 7x8=56n

wavelength divides in half and speed stays the same.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia