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

Question

inna [77]

3 years ago

7

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?

Chemistry

2 answers:

Karo-lina-s [1.5K] · Answer 1 · 2022-02-13T11:31:05+03:00

Number of photons can be calculated by dividing the needed energy by the energy per photon.

The minimum energy needed is given as 2 x 10^-17 joules
Energy per photon = hc / lambda where h is planck's constant, c is the speed of light and lambda is the wavelength
Energy per photon = (<span>6.626 x 10^-34 x 3 x 10^8) / (475 x 10^-9)
= 4.18 x 10^-19 J

number of photons = (2 x 10^-17) / (4.18 x 10^-19)
= 47.79 photons which is approximately 48 photons</span>

Sonja [21] · Answer 2 · 2022-02-13T13:01:05+03:00

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

$\large{\boxed{\bold{E\:=\:h\:.\:f}}}$