Why do x-ray technicians stand behind a shield when giving x-rays to patients? a) because large doses of x-rays cause blindness b) because they can more accurately see the patient's bones c) because they need to protect themselves from patient disease d) because large doses of x-rays are known to cause cell damage and cancers

X-ray technicians stand behind a shield when giving X-rays to patients because large doses of X-rays are known to cause cell damage and cancers.

D

Explanation:

Electromagnetic radiations like x-rays, alpha rays and other cosmic rays are harmful to human health and tissues to some extent when it is exposed for long time.

The x-rays are created when highly accelerated electrons hit the metal leading to ejection of electrons from its shell.

The x-rays are highly penetrate able but it cannot penetrate bones. So it is mostly used for getting scans of bones.

X-rays can penetrate cells and when exposed for large time in large doses it can harm the cell by damaging them or by creating cancer cells.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.