Waves
Help Questions
MCAT Physical › Waves
Unpolarized light passes through three polarizing filters. The angle between the first and second filters is 45o. The angle between the second and third filters is also 45o. What is the relationship between the intensity of light emerging from the third filter, , and the incident intensity,
?
No light passes through the third filter
Explanation
Going through the first filter, the intensity of initially unpolarized light decreases by 1/2, so . For each filter after the first, the intensity decreases by an additional factor of
, where
is the angle between adjacent polarizers. So, after the second filter, we have can see that
. Similarly, after the third filter, we have
.
An incandescent light bulb is shown through a glass prism. The certain wavelength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
What type of light is produced by the incandescent light bulb?
Visible
IR
Ultraviolet
Gamma
Explanation
Incandescent light bulbs produce visible light of all wavelengths. The mix of red, orange, yellow, green, blue, indigo, and violet (ROYGBIV) give the light its characteristic white appearance. For the MCAT, it is important to know the relative wavelengths of light for the visible spectrum (390 – 700nm) and where visiable wavelengths fit into the overall spectrum of electromagnetic radiation. From longest wavelength to shortest, the sequence of wavelengths is listed below.
Radio > Microwaves > Infrared > Visible > Ultraviolet > X-Rays > Gamma Rays
Unpolarized light passes through three polarizing filters. The angle between the first and second filters is 45o. The angle between the second and third filters is also 45o. What is the relationship between the intensity of light emerging from the third filter, , and the incident intensity,
?
No light passes through the third filter
Explanation
Going through the first filter, the intensity of initially unpolarized light decreases by 1/2, so . For each filter after the first, the intensity decreases by an additional factor of
, where
is the angle between adjacent polarizers. So, after the second filter, we have can see that
. Similarly, after the third filter, we have
.
An incandescent light bulb is shown through a glass prism. The certain wavelength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
What type of light is produced by the incandescent light bulb?
Visible
IR
Ultraviolet
Gamma
Explanation
Incandescent light bulbs produce visible light of all wavelengths. The mix of red, orange, yellow, green, blue, indigo, and violet (ROYGBIV) give the light its characteristic white appearance. For the MCAT, it is important to know the relative wavelengths of light for the visible spectrum (390 – 700nm) and where visiable wavelengths fit into the overall spectrum of electromagnetic radiation. From longest wavelength to shortest, the sequence of wavelengths is listed below.
Radio > Microwaves > Infrared > Visible > Ultraviolet > X-Rays > Gamma Rays
An incandescent light bulb is shown through a glass prism. The certain wavelength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
What type of light is produced by the incandescent light bulb?
Visible
IR
Ultraviolet
Gamma
Explanation
Incandescent light bulbs produce visible light of all wavelengths. The mix of red, orange, yellow, green, blue, indigo, and violet (ROYGBIV) give the light its characteristic white appearance. For the MCAT, it is important to know the relative wavelengths of light for the visible spectrum (390 – 700nm) and where visiable wavelengths fit into the overall spectrum of electromagnetic radiation. From longest wavelength to shortest, the sequence of wavelengths is listed below.
Radio > Microwaves > Infrared > Visible > Ultraviolet > X-Rays > Gamma Rays
Unpolarized light passes through three polarizing filters. The angle between the first and second filters is 45o. The angle between the second and third filters is also 45o. What is the relationship between the intensity of light emerging from the third filter, , and the incident intensity,
?
No light passes through the third filter
Explanation
Going through the first filter, the intensity of initially unpolarized light decreases by 1/2, so . For each filter after the first, the intensity decreases by an additional factor of
, where
is the angle between adjacent polarizers. So, after the second filter, we have can see that
. Similarly, after the third filter, we have
.
At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.
How does the speed of sound in the summer (30oC) compare to the speed of sound in the winter (9oC)?
Speed of sound in summer is 1.04 times the speed of sound in winter
Speed of sound in summer is 1.2 times the speed of sound in winter
Speed of sound in summer is equal to the speed of sound in winter
Speed of sound in summer is 0.81 times the speed of sound in winter
Explanation
This question asks us to use information provided in the paragraph about how the speed of sound varies with temperature. We can see from the relationship provided that in warmer temperatures the speed of sound is faster. This intuitively makes sense—hotter temperatures mean that air molecules are moving around more, and thus have less resistance to compression or rarefaction by a propagating sound wave. Now that we have a qualitative understanding, we need to compute the ratio of the velocities.
Waves hit a beach every three seconds. The horizontal distance between an adjacent maximum and minimum is one meter. What is the speed of the waves?
Explanation
Wave velocity is given by the product of frequency and wavelength:
In the question, we are given the period (waves per second). To find the frequency, we will need to take the reciprocal of the period.
Using the values given in the question, we can find the velocity of the waves. The wavelength is twice the distance between adjacent maxima and minima, making our wavelength two meters.
Waves hit a beach every three seconds. The horizontal distance between an adjacent maximum and minimum is one meter. What is the speed of the waves?
Explanation
Wave velocity is given by the product of frequency and wavelength:
In the question, we are given the period (waves per second). To find the frequency, we will need to take the reciprocal of the period.
Using the values given in the question, we can find the velocity of the waves. The wavelength is twice the distance between adjacent maxima and minima, making our wavelength two meters.
An incandescent light bulb is shown through a glass prism. The certain wavlength of the light is then directed into a glass cuvette containing an unknown concentration of protein. Commonly, this process is called spectroscopy and is used to determine the concentrations of DNA, RNA, and proteins in solutions. The indices of reflection of air, glass, and the solution are 1, 1.5, and 1.3, respectively.
Light is a __________.
particle and a wave
particle
wave
particle or wave, depending on wavelength
Explanation
As Einstein determined, light has properties of both a particle and a wave. In the particle sense, it has mass, velocity, and momentum. The wave property of light allows for diffraction, and constructive and destructive interference. For the MCAT, it is important to know that the photon (the particle of light) has both particle and wave properties. In fact, all objects have both particle and wave properties; however, their wave property becomes less obvious with increasing mass.