X-ray
Explanation:
X-rays are used medically by doctors to image the interior of the human body but can cause cell damage.
X-rays are energetic radiations that are classified as ionizing radiations.
They penetrate the skin and body tissues.
- X-rays were discovered by Wilhelm Conrad Röentgen In Germany in the year 1895.
- The rays have a wide range of application today.
- They are used in x-ray therapy to fight cancerous cells in the body.
Learn more:
X-ray brainly.com/question/6507143
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also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus.
Explanation:

The maximum wavelength of light that can cause this reaction is 420 nm.
a) The wavelength given lies in the range of visible light range that is from 400 nano meters to 700 nano meters.
The light with wavelength of 420 nm is found in the range of visible light.
b)The maximum strength of a bond :

where,
E = energy of photon = Energy required to break single molecule of nitrogen dioxide
h = Planck's constant = 
c = speed of light = 
= wavelength = 


Energy required to break 1 mole of nitrogen dioxide molecules:


(1 J = 0.001 kJ )
285.13 is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light.
c) the photodissociation reaction showing Lewis-dot structures is given in an image attached.
<span>A. the sum of the protons and neutrons in one atom of the element</span>