Why the welding personel have to use special spectacles?

Why do gases have two specific heats?

A person can see distinctly up to a distance of 2 m and no further. To see distinctly up to a long distance what type of spectacles should he use? What will be the power of the lens of the spectacles?

The least distance of vision of a longsighted person is 60cm. By using a spectacle lens, this distance is reduced to 12cm. The power of the lens is

A short-sighted person can read a book only up to 15 cm from his eyes. To read a book placed at a distance of 25 cm from him what type of spectacles should he use? What be the power of the spectacles?

Parasitic fungi have specialized hyphae called

Why do polymers not have a specific molecular mass?

A person can see distinctly any object situated in between the distance 50 cm and 300 cm. what type of spectacles are to used (ii) to bring the least distance of distinct vision at 25 cm ? What will be the rangs of distinct vision in each pair of spectacles?