Chapter 7
Light in Biology and Medicine
“Researchers in this field have thrown great darkness on the
subject, and, it is probable that if they continue, we shall soon
know nothing about it.”
— Mark Twain
Summary Humans were unaware of radio waves until 1885, when Heinrich Hertz
detected them after Maxwell’s prediction in 1864. We now realize how important
all electromagnetic waves are in the Universe and in their actions on life forms,
including the effects of infrared ‘heat’ waves, microwaves, visible light, ultraviolet
light, X-rays, and gamma rays. Today, our technological society utilizes all such
waves, including for biological research and medical applications.
7.1 Electromagnetic Waves
James Clerk Maxwell, using the logic of his theory of electromagnetism, predicted
the existence of self-sustaining electromagnetic waves, with all possible frequencies. In empty space, the curl of each side of Eq. (6.2), combined with Eq. (6.1)
gives
1
c 2
∂ 2 E
∂t 2 − ∇
2 E = 0 .
(7.1)
Similarly, Eqs. (6.4) and (6.3) give
1
c 2
∂ 2 B
∂t 2 − ∇
2 B = 0 .
(7.2)
These are wave equations, just like the ones we encountered for sound waves.
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_7
205
Light in Biology and Medicine
“Researchers in this field have thrown great darkness on the
subject, and, it is probable that if they continue, we shall soon
know nothing about it.”
— Mark Twain
Summary Humans were unaware of radio waves until 1885, when Heinrich Hertz
detected them after Maxwell’s prediction in 1864. We now realize how important
all electromagnetic waves are in the Universe and in their actions on life forms,
including the effects of infrared ‘heat’ waves, microwaves, visible light, ultraviolet
light, X-rays, and gamma rays. Today, our technological society utilizes all such
waves, including for biological research and medical applications.
7.1 Electromagnetic Waves
James Clerk Maxwell, using the logic of his theory of electromagnetism, predicted
the existence of self-sustaining electromagnetic waves, with all possible frequencies. In empty space, the curl of each side of Eq. (6.2), combined with Eq. (6.1)
gives
1
c 2
∂ 2 E
∂t 2 − ∇
2 E = 0 .
(7.1)
Similarly, Eqs. (6.4) and (6.3) give
1
c 2
∂ 2 B
∂t 2 − ∇
2 B = 0 .
(7.2)
These are wave equations, just like the ones we encountered for sound waves.
© Springer Nature Switzerland AG 2020
W. C. Parke, Biophysics, https://doi.org/10.1007/978-3-030-44146-3_7
205