Physics in our Life!

Astronauts use wireless waves in communication ?
Because sound waves are mechanical waves cannot travel through space, while wireless waves are electromagnetic waves that can travel through space .

Several instruments are in a state of resonance?
Means that they are vibrating with equal frequencies at the same time .

The tone produced by different musical instruments differ from each other ?
Because each instrument produces the fundamental tone plus its overtones also they different in characteristic sound quality .

The cuboid neither deviated nor disperses white light ?
Because it's considered as two prisms identical in refracting angle "A" and in material (R.I.) but place in opposite directions to each other, so deviation or dispersion made by one of them is cancelled by the other .

Reflecting prisms are preferred than metallic mirrors ?
Because they perform 100% reflection, while mirrors may lose luster .

The face of the prism upon which light falls is covered with a thin layer of cryolite ( aluminium  fluoride ) or magnesium fluoride ?
To minimize dissipation of light ( or increase efficiency of reflection  ) because cryolite has an intermediate value between glass and air.

The incident ray passing through the optical (vision) center of lens is undeviated and undispersed ?
Because the middle section of the lens is considered as a rectangular block formed of two opposite prisms that are equal in (n) and (A), therefore, the emergent ray becomes parallel to incident one .

Convex lens converges rays, while concave lens diverges rays ?
Because lens is considered as if formed of two prisms that are joined at the base ( in convex one ) and joined at the apex ( in concave lens ), so incident rays approach the base of the prism on which the rays are falling.