Which statement is true about the part of the electromagnetic spectrum that is divided into seven ranges of wavelengths?

a. it is one of three parts visible to the human eye.
b. it is the only part visible to the human eye.
c. it is one of two parts visible to the human eye.
d. it cannot be seen by the human eye unless it rains.

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.