Here you are invited to explore the process of human vision. (a) The flux of visible photons reaching Earth from the North Star is about 4 x 103 mm-2s-1. Of these photons, 30 per cent are absorbed or scattered by the atmosphere and 25 per cent, of the surviving photons are scattered by the surface of the cornea of the eye. A further 9 per cent ar absorbed inside the cornea. The area of the pupil at night is about 40 mm2 and the response t ime of the eye is about 0.1 s. Of the photons passing through the pupil, about 43 per cent are absorbed in the ocular medium. How many photons from the North Star are focused on to the retina in 0.1 s? For a continuation of this story, see R. W. Rodieck, The first steps in seeing, Sinauer (1998). (b) In the free-electron molecular orbital theory of electronic structure, the π electrons in a conjugated molecule are treated as non-interacting particles in a box of length equal to the length of the conjugated system. On the basis of this model, at what wavelength would you expect all trans-retinal to absorb? Take the mean carboncarbon bond length to be 140 pm.
Atomic Spectra
According to the Bohr model of an atom, the electron in an atom moves around a nucleus in fixed orbits with specific energies known as energy levels. The orbital energies are quantized. The electrons remain in these energy levels until they emit or absorb a photon of a particular wavelength, the quantum of energy. If the electron emits a photon, it then falls back to a lower energy level, and if it absorbs a photon, the electron rises to higher energy levels. The photons released or absorbed in these transitions of an electron are studied and analyzed on a screen as atomic spectra.
Ruby Lasers
Lasers are devices that emit light using atoms or molecules at a certain wavelength and amplify the light to produce a narrow beam of radiation. It works as per the principle of electromagnetic radiation. Their source of emission contains the same frequency and same phase. It was invented in the year 1960 by the great noble scientist, Theodore Maiman.
Balmer Series
The spectrum of frequency observed when electromagnetic radiation is emitted from an atom when it goes from higher energy state to lower state, is known as emission spectrum. This transition occurs when an excited electron moves from higher to lower state. It has many possible electron transitions and each transition has a specific energy difference.
Emission Spectrum
Every state of matter tries to be at minimum potential energy or it can be said that the atoms of element/ substance arrange themselves such that overall energy is minimum.
Here you are invited to explore the process of human vision. (a) The flux of visible photons reaching Earth from the North Star is about 4 x 103 mm-2s-1. Of these photons, 30 per cent are absorbed or scattered by the atmosphere and 25 per cent, of the surviving photons are scattered by the surface of the cornea of the eye. A further 9 per cent ar absorbed inside the cornea. The area of the pupil at night is about 40 mm2 and the response t ime of the eye is about 0.1 s. Of the photons passing through the pupil, about 43 per cent are absorbed in the ocular medium. How many photons from the North Star are focused on to the retina in 0.1 s? For a continuation of this story, see R. W. Rodieck, The first steps in seeing, Sinauer (1998). (b) In the free-electron molecular orbital theory of electronic structure, the π electrons in a conjugated molecule are treated as non-interacting particles in a box of length equal to the length of the conjugated system. On the basis of this model, at what wavelength would you expect all trans-retinal to absorb? Take the mean carboncarbon bond length to be 140 pm.
Trending now
This is a popular solution!
Step by step
Solved in 5 steps with 5 images
