The human eye is a complex sensing device for visible light. The optic nerve needs a minimum of 2.0 × 10−17 J of energy to trigg
er a series of impulses that eventually reach the brain. How many photons of blue light (475 nm) are needed?
2 answers:
The number of photons needed to get the energy to trigger a series of impulses that eventually reaches the brain is: 48.7 photons
<h3><em>Further explanation</em></h3>
The photoelectric effect is an electron coming out of a metal because of electromagnetic radiation
One type of electromagnetic radiation is light
Electrons can come out of metal because they absorb electromagnetic energy radiated on metals. There is also kinetic energy released from metal, which is according to the equation:
E = hf - hfo
fo = the threshold frequency of electromagnetic waves
Radiation energy is absorbed by photons
The energy in one photon can be formulated as
Where
h = Planck's constant (6,626.10⁻³⁴ Js)
f = Frequency of electromagnetic waves
f = c / λ
c = speed of light
= 3.10⁸
λ = wavelength
Known wavelength 475 nm
475 nm = 475.10⁻⁹ m
We put it in the formula to find this light energy E = h. f
E = h. c /λ
E =: 6,626.10⁻³⁴. 3.10⁸ / 475 .10⁻⁹ m
E = 4.1.10⁻¹⁹
Because this is 1 photon energy, while the minimum energy required is 2.0 × 10⁻¹⁷ J, the number of photons needed is:
number of photons = 2.0 × 10−17 J: 4.1.10⁻¹⁹
number of photons = 48.7
<h3><em>Learn more</em></h3>Electromagnetic radiation with wavelength of 745 nm
The energy of a photon
The equation E = hf
the approximate energy of a photon
The equation for photon energy
the wavelength of a photon whose energy is twice
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