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Ch.5 - Periodicity & Electronic Structure of Atoms

Chapter 5, Problem 26c

Two electromagnetic waves are represented below.

(c) Which wave represents yellow light, and which represents infrared radiation?

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Hey everyone, we're asked to identify the false statement and correct it. First. Looking at a we have ultraviolet light has a smaller wavelength than microwaves. First. Let's go ahead and think about our electromagnetic spectrum. Looking at our spectrum, we know that as we move to the left, our energy is going to increase. And as we move to the right, our wavelength is going to increase. And in terms of our microwaves and our ultraviolet light, microwaves are on our right side of our spectrum, followed by infrared, followed by our ultraviolet, followed by our X rays. To name a few. Looking at our spectrum, we can see that ultraviolet light does in fact have a smaller wavelength than microwaves. So A is going to be correct. Looking at B, we have the glow from burning wood, black lights and radio frequencies are all forms of electromagnetic radiation. Starting off with our glow from burning wood, we know that this is going to be visible light. And also looking at our black lights, this is also going to be visible light which is in fact a part of our spectrum. And for radio frequencies, we know that this is going to be radio waves. So answer choice B is also correct looking at C, we have the wavelength of radiation decreases as frequency increases. This statement is going to be correct, since our formula is speed of light is equal to our wavelength times our frequency. And when we change our formula to equal frequency, we end up with frequency, equal speed of light over our wavelength. And as we can see right here, frequency and wavelength are inversely proportional to one another. And lastly, looking at D, we have the speed of electromagnetic radiation in a vacuum increases as the frequency of light increases. So this statement is incorrect and is going to be our answer. The reason why is because our speed of electromagnetic radiation in a vacuum will remain constant, And that's because our speed of light is equal to 3.0 times 10 to the 8th m/s. So I hope this made sense and let us know if you have any questions.