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Ch 33: The Nature and Propagation of Light
Chapter 33, Problem 33

Light of a certain frequency has a wavelength of 526 nm in water. What is the wavelength of this light in benzene?

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Identify the refractive indices of water and benzene. The refractive index (n) is a measure of how much the speed of light is reduced inside a medium compared to the speed of light in a vacuum.
Use the formula for the speed of light in a medium: v = c/n, where c is the speed of light in vacuum and v is the speed of light in the medium. Since the frequency (f) of light remains constant when transitioning between media, the relationship between wavelength (\(\lambda\)) and speed is given by \(\lambda = v/f\).
Express the wavelength in water in terms of its refractive index: \(\lambda_{water} = \frac{c}{n_{water} \times f}\).
Set up the equation to find the wavelength in benzene using its refractive index: \(\lambda_{benzene} = \frac{c}{n_{benzene} \times f}\).
Since the frequency of light does not change, equate the expressions for speed of light in both media and solve for \(\lambda_{benzene}\) using the known value of \(\lambda_{water}\) and the refractive indices: \(\lambda_{benzene} = \lambda_{water} \times \frac{n_{water}}{n_{benzene}}\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Wavelength and Frequency Relationship

The wavelength of light is inversely related to its frequency, as described by the equation c = λν, where c is the speed of light, λ is the wavelength, and ν is the frequency. This means that as the wavelength increases, the frequency decreases, and vice versa. Understanding this relationship is crucial for converting between different media.
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Circumference, Period, and Frequency in UCM

Refraction and Snell's Law

Refraction occurs when light passes from one medium to another, changing its speed and direction. Snell's Law describes this phenomenon mathematically, stating that n1 * sin(θ1) = n2 * sin(θ2), where n is the refractive index of the media and θ is the angle of incidence or refraction. This principle is essential for determining how the wavelength of light changes in different substances.
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Refractive Index

The refractive index of a medium is a dimensionless number that describes how much light slows down in that medium compared to a vacuum. It is defined as n = c/v, where c is the speed of light in a vacuum and v is the speed of light in the medium. The refractive index affects the wavelength of light, as the wavelength in a medium is given by λ_medium = λ_vacuum/n.
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Related Practice
Textbook Question
As shown in Fig. E33.11

, a layer of water covers a slab of material X in a beaker. A ray of light traveling upward follows the path indicated. Using the information on the figure, find (b) the angle the light makes with the normal in the air.
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Textbook Question
The indexes of refraction for violet light λ = 400 nm2 and red light λ= 700 nm2 in diamond are 2.46 and 2.41, respectively. A ray of light traveling through air strikes the diamond surface at an angle of 53.5° to the normal. Calculate the angular separation between these two colors of light in the refracted ray.
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Textbook Question
A light beam travels at 1.94 * 10^8 m/s in quartz. The wavelength of the light in quartz is 355 nm. (b) If this same light travels through air, what is its wavelength there?
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Textbook Question
(a) A tank containing methanol has walls 2.50 cm thick made of glass of refractive index 1.550. Light from the outside air strikes the glass at a 41.3° angle with the normal to the glass. Find the angle the light makes with the normal in the methanol. (b) The tank is emptied and refilled with an unknown liquid. If light incident at the same angle as in part (a) enters the liquid in the tank at an angle of 20.2° from the normal, what is the refractive index of the unknown liquid?
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Textbook Question
Unpolarized light with intensity I0 is incident on two polarizing filters. The axis of the first filter makes an angle of 60.0° with the vertical, and the axis of the second filter is horizontal. What is the intensity of the light after it has passed through the second filter?
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Textbook Question
A beam of unpolarized light of intensity I0 passes through a series of ideal polarizing filters with their polarizing axes turned to various angles as shown in Fig. E33.27. (b) If we remove the middle filter, what will be the light intensity at point C?
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