BIO Reflective Coatings and Herring. Herring and related fish have a brilliant silvery appearance that camouflages them while they are swimming in a sunlit ocean. The silveriness is due to platelets attached to the surfaces of these fish. Each platelet is made up of several alternating layers of crystalline guanine (n = 1.80) and of cytoplasm (n = 1.333, the same as water), with a guanine layer on the outside in contact with the surrounding water (Fig. P35.50). In one typical platelet, the guanine layers are 74 nm thick and the cytoplasm layers are 100 nm thick. (a) For light striking the platelet surface at normal incidence, for which vacuum wavelengths of visible light will all of the reflections R1, R2, R3, and R5, shown in Fig. P35.50, be approximately in phase? If white light is shone on this platelet, what color will be most strongly reflected (see Fig. 32.4)? The surface of a herring has very many platelets side by side with layers of different thickness, so that all visible wavelengths are reflected. (b) Explain why such a “stack” of layers is more reflective than a single layer of guanine with cytoplasm underneath. (A stack of five guanine layers separated by cytoplasm layers reflects more than 80% of incident
Figure P35.50
Want to see the full answer?
Check out a sample textbook solutionChapter 35 Solutions
University Physics with Modern Physics (14th Edition)
Additional Science Textbook Solutions
College Physics (10th Edition)
Applied Physics (11th Edition)
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
The Cosmic Perspective
Introduction to Electrodynamics
Cosmic Perspective Fundamentals
- A colloid consists of particles of one type of substance dispersed in another substance. Suspensions of electrically charged microspheres (microscopic spheres, such as polystyrene) in a liquid such as water can form a colloidal crystal when the microspheres arrange themselves in a regular repeating pattern under the influence of the electrostatic force. Colloidal crystals can selectively manipulate different wavelengths of visible light. Just as we can study crystalline solids by using Bragg reflection of x rays, we can study colloidal crystals through Bragg scattering of visible light from the regular arrangement of charged microspheres. Because the light is traveling through a liquid when it experiences the path differences that lead to constructive interference, it is the wavelength in the liquid that determines the angles at which Bragg reflections are seen. In one experiment, laser light with a wavelength in vacuum of 650 nm is passed through a sample of charged polystyrene…arrow_forwardA colloid consists of particles of one type of substance dispersed in another substance. Suspensions of electrically charged microspheres (microscopic spheres, such as polystyrene) in a liquid such as water can form a colloidal crystal when the microspheres arrange themselves in a regular repeating pattern under the influence of the electrostatic force. Colloidal crystals can selectively manipulate different wavelengths of visible light. Just as we can study crystalline solids by using Bragg reflection of x rays, we can study colloidal crystals through Bragg scattering of visible light from the regular arrangement of charged microspheres. Because the light is traveling through a liquid when it experiences the path differences that lead to constructive interference, it is the wavelength in the liquid that determines the angles at which Bragg reflections are seen. In one experiment, laser light with a wavelength in vacuum of 650 nm is passed through a sample of charged polystyrene…arrow_forwardThe coordinates of the four I atoms in the unit cell of KIO4 are (0,0,0), (0,1/2,1/2), (1/2,1/2,1/2), (1/2,0, 3/4). By calculating the phase of the I reflection in the structure factor, show that the I atoms contribute no net intensity to the (114) reflection.arrow_forward
- 4arrow_forwardThe skin reflects most visible and IR-A (near-infrared) radiation. The epidermis is highly absorbing at UV-B and UV-C wavelengths and at IR-B and IR-C wavelengths. True or Falsearrow_forwardSalt absorbs in the infrared. The complex dielectric constant at wavelength 60µm is -16.8 + i91.4. Calculate the absorption coefficient and the reflectivity at normal incidence at stated wavelength, knowing that 5. E = Er + iɛ¡ ɛ = n? n = n, + in; 2wnį a = 1 |n R = In + 1 where e is the dielectric constant, n is the refractive index, a is the absorption coefficient and R is the reflectivity.arrow_forward
- Building contractors often install double-glazed windows to prevent thermal energy (heat) from entering or exiting a building. In addition to being effective insulators, such windows present interesting optical effects. In the figure, a double-glazed window consists of two identical panes of glass (ng = 1.54), each yg = 22.0 mm thick, separated by an air gap of y₁ = 17.6 mm. Use na = 1.00 for the index of refraction of air. If light incident on the glass makes an angle of d = 40.00° with respect to the glass, find the shift in path Ax as the light enters the room. Ax = glass air glass mmarrow_forwardThe Bragg angle for a certain reflection from a powder specimen of copper is 47.75 degrees at a Temperature of 293 K and 46.60 degrees at 1273 K. Calculate the coefficient of linear thermal expansion of copper. O A. 1.91 X 106 K-1 В. 2.81 X 106 к1 O C. 1.91 X 105 K1 С. O D. 2.81 X 10-5 K-1arrow_forwardThe index of refraction of a glass rod is 1.48 at T = 20.0°C and varies linearly with temperature, with a coefficient of 2.50 x 10-5C⁰-1. The coefficient of linear expansion of the glass is 5.00 x 10-6C⁰-1. At 20.0 °C the length of the rod is 2.80 cm. A Michelson interferometer has this glass rod in one arm, and the rod is being heated so that its temperature increases at a rate of 5.00 C°/min. The light source has wavelength λ = 569 nm, and the rod initially is at T = 20.0°C. Part A How many fringes cross the field of view each minute? ΔΝ = Submit ΤΙ ΑΣΦ Request Answer < Return to Assignment Provide Feedback ? fringes/minutearrow_forward
- Structure factor of diamond. The crystal structure of diamond is described in Chapter 1. The basis consists of eight atoms if the cell is taken as the conventional cube. (a) Find the structure factor S of this basis. (b) Find the zeros of S and show that the allowed reflections of the diamond structure satisfy v, + U2+ Uz = 4n, where all indices are even and n is any integer, or else all indices are odd (Fig. 18). (Notice that h, k, l may be written for v, v2, Uz and this is often done.)arrow_forward5. Light can be described as an electromagnetic wave. The optical lenses also can be modeled as dielectric lenses which can be used to collimate electromagnetic fields. The following figure shows the circular surface in the left and planar surface in the right of the lens. Let E1(r, ø, z) = {10, -6, 0}, what must be the dielectric constant of the lens in order that E3(r, ø, z) in region 3 is parallel to the x-axis? y. To 45° 3arrow_forwardBiologists use optical tweezers to manipulate micron-sized objects using a beam of light. In this technique, a laser beam is focused to a very small-diameter spot. Because small particles are attracted to regions of high light intensity, the focused beam can be used to “grab” onto particles and manipulate them for various experiments. In one experiment, a 10 mW laser beam is focused to a spot that has a diameter of 0.62 μm.a. What is the intensity of the light in this spot?b. What is the amplitude of the electric field?arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning