9. Quantum Mechanics

The Energy of Light

9. Quantum Mechanics

The Energy of Light

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The Energy of Light Example 1

The Energy of Light Example 2

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04:39

What Is Light?

Kurzgesagt – In a Nutshell

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06:08

What the HECK is a Photon?!

Why Does Light REALLY Bend?

Why Doesn't Light Have Mass?

Light: Crash Course Astronomy #24

What is Light? Maxwell and the Electromagnetic Spectrum

Professor Dave Explains

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Showing 7 of 7 videos

Practice this topic

Multiple Choice

Calculate the energy (in nJ) of a photon emitted by a mercury lamp with a frequency of 6.88 x 10¹⁴ Hz.

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Multiple Choice

A light ray has a wavelength that is 835 µm contains 6.32 x 10^-3 J of energy. How many photons does this light ray have?

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Multiple Choice

How much energy (in kJ) do 4.50 moles of photons contain at a wavelength of 705 nm?

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Textbook Question

Which wave corresponds to higher energy radiation? (LO 5.1) (a)

(b)

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Textbook Question

What is the energy (in kJ) of one mole of photons of ultraviolet light with a wavelength of 85 nm? (LO 5.3) (a) 1.4 * 10-6 kJ (b) 1.4 * 103 kJ (c) 2.4 * 1014 kJ (d) 2.4 * 10-15 kJ

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Textbook Question

Where does the energy come from to evaporate the esti- mated 425,000 km3 of water that annually leaves the oceans, as illustrated here? [Section 18.3]

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Textbook Question

The dissociation energy of a carbon-bromine bond is typically about 276 kJ/mol. (a) What is the maximum wavelength of photons that can cause C-Br bond dissociation?

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Textbook Question

(b) Use the energy requirements of these two pro- cesses to explain why photodissociation of oxygen is more important than photoionization of oxygen at altitudes below about 90 km.

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Textbook Question

If human height were quantized in 1-cm increments, what would happen to the height of a child as she grows up: (i) the child's height would never change, (ii) the child's height would continuously increase, (iii) the child's height would increase in jumps of 6 cm, or (iv) the child's height would increase in 'jumps' of 1 cm at a time?

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Textbook Question

(a) Calculate the energy of a photon of electromagnetic radiation whose frequency is 2.94 * 1014 s - 1.

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Textbook Question

(b) Calculate the energy of a photon of radiation whose wavelength is 413 nm.

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Textbook Question

(b) What is the energy of one of these photons?

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Textbook Question

(c) The laser pointer emits light because electrons in the material are excited (by a battery) from their ground state to an upper excited state. When the electrons return to the ground state, they lose the excess energy in the form of 532-nm photons. What is the energy gap between the ground state and excited state in the laser material?

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Textbook Question

An AM radio station broadcasts at 1000 kHz and its FM partner broadcasts at 100 MHz. Calculate and compare the energy of the photons emitted by these two radio stations.

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Textbook Question

One type of sunburn occurs on exposure to UV light of wavelength in the vicinity of 325 nm. (d) These UV photons can break chemical bonds in your skin to cause sunburn—a form of radiation damage. If the 325-nm radiation provides exactly the energy to break an average chemical bond in the skin, estimate the average energy of these bonds in kJ>mol.

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Textbook Question

One type of sunburn occurs on exposure to UV light of wavelength in the vicinity of 325 nm. (c) How many photons are in a 1.00 mJ burst of this radiation?

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Textbook Question

Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH2O + hn ¡ CHO + H The maximum wavelength of light that can cause this reac- tion is 335 nm. (b) What is the maximum strength of a bond, in kJ>mol, that can be bro- ken by absorption of a photon of 335-nm light?

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Textbook Question

Calculate the energy of a photon of electromagnetic radiation at each of the wavelengths indicated in Problem 39. a. 632.8 nm (wavelength of red light from helium–neon laser) b. 503 nm (wavelength of maximum solar radiation) c. 0.052 nm (wavelength contained in medical X-rays)

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Textbook Question

Calculate the energies of the following waves in kilojoules per mole, and tell which member of each pair has the higher value. (a) An FM radio wave at 99.5 MHz and an AM radio wave at 1150 kHz

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Textbook Question

Calculate the energy of a photon of electromagnetic radiation at each of the frequencies indicated in Problem 40. a. 100.2 MHz (typical frequency for FM radio broadcasting) b. 1070 kHz (typical frequency for AM radio broadcasting) (assume four significant figures) c. 835.6 MHz (common frequency used for cell phone communication)

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Textbook Question

A laser pulse with wavelength 532 nm contains 3.85 mJ of energy. How many photons are in the laser pulse?

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Textbook Question

A heat lamp produces 32.8 watts of power at a wavelength of 6.5 µm. How many photons are emitted per second? (1 watt = 1 J/s)

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Textbook Question

Determine the energy of 1 mol of photons for each kind of light. (Assume three significant figures.) a. infrared radiation (1500 nm)

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Textbook Question

What is the energy of each of the following photons in kilojoules per mole? (a) v = 5.97 * 1019 s-1 (b) v = 1.26 * 106 s-1 (c) = 2.57 * 102 m

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Textbook Question

How much energy is contained in 1 mol of each? a. X-ray photons with a wavelength of 0.135 nm b. g-ray photons with a wavelength of 2.15 * 10-5 nm

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Textbook Question

According to the equation for the Balmer line spectrum of hydrogen, a value of n = 3 gives a red spectral line at 656.3 nm, a value of n = 4 gives a green line at 486.1 nm, and a value of n = 5 gives a blue line at 434.0 nm. Calculate the energy in kilojoules per mole of the radiation corresponding to each of these spectral lines.

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Textbook Question

The rate of solar energy striking Earth averages 168 watts per square meter. The rate of energy radiated from Earth's surface averages 390 watts per square meter. Comparing these numbers, one might expect that the planet would cool quickly, yet it does not. Why not?

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Textbook Question

Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because these kinds of radiation carry enough energy to break bonds within the molecules. A typical carbon–carbon bond requires 348 kJ>mol to break. What is the longest wavelength of radiation with enough energy to break carbon–carbon bonds?

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Textbook Question

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. The change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. The minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kJ>mol. Calculate the longest wavelength visible to the human eye.

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Textbook Question

Ionization involves completely removing an electron from an atom. How much energy is required to ionize a hydrogen atom in its ground (or lowest energy) state? What wavelength of light contains enough energy in a single photon to ionize a hydrogen atom?

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Textbook Question

The concentration of H2O in the stratosphere is about 5 ppm. It undergoes photodissociation according to: H2O1g2 ¡ H1g2 + OH1g2 (b) Using Table 8.3, calculate the wavelength required to cause this dissociation.

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Textbook Question

If a sample of calcium chloride is introduced into a nonluminous flame, the color of the flame turns to orange ('flame test'). The light is emitted because calcium atoms become excited; their return to the ground state results in light emission. (b) What is the energy of 1.00 mol of these photons (a mole of photons is called an Einstein)?

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Textbook Question

The watt is the derived SI unit of power, the measure of energy per unit time: 1 W = 1 J>s. A semiconductor laser in a DVD player has an output wavelength of 650 nm and a power level of 5.0 mW. How many photons strike the DVD surface during the playing of a DVD 90 minutes in length?

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Textbook Question

A 5.00-mL ampule of a 0.100-M solution of naphthalene in hexane is excited with a flash of light. The naphthalene emits 15.5 J of energy at an average wavelength of 349 nm. What percentage of the naphthalene molecules emitted a photon?

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Textbook Question

A laser produces 20.0 mW of red light. In 1.00 hr, the laser emits 2.29 * 1020 photons. What is the wavelength of the laser?

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Textbook Question

A particular laser consumes 150.0 watts of electrical power and produces a stream of 1.33 * 1019 1064-nm photons per second. What is the percent efficiency of the laser in converting electrical power to light?

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Textbook Question

Consider the electronic structure of the element bismuth. (a) The first ionization energy of bismuth is Ei1 = +703 kJ/ mol. What is the longest possible wavelength of light that could ionize an atom of bismuth?

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Textbook Question

A photovoltaic cell contains a p–n junction that that converts solar light to electricity. An optimum semiconductor would have its band-gap energy matched to the wavelength of maximum solar intensity at the Earth's surface. (b) Which of the following semiconductors absorb at a wavelength matched with maximum solar intensity? CdTe with a band-gap energy of 145 kJ/mol or ZnSe with a band-gap energy of 248 kJ/mol.

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Textbook Question

Iron is commonly found as Fe, Fe2+, and Fe3+. (c) The third ionization energy of Fe is Ei3 = +2952 kJ/mol. What is the longest wavelength of light that could ionize Fe2+1g2 to Fe3+1g2?

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Textbook Question

One watt (W) is equal to 1 J/s. Assuming that 5.0% of the energy output of a 75 W light bulb is visible light and that the average wavelength of the light is 550 nm, how many photons are emitted by the light bulb each second?

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Textbook Question

Microwave ovens work by irradiating food with microwave radiation, which is absorbed and converted into heat. Assum-ing that radiation with l = 15.0 cm is used, that all the energy is converted to heat, and that 4.184 J is needed to raise the temperature of 1.00 g of water by 1.00 °C, how many photons are necessary to raise the temperature of a 350 mL cup of water from 20 °C to 95 °C?

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Textbook Question

Red light with a wavelength of 660 nm from a 3.0 mW diode laser shines on a solar cell. (b) How much current (in amperes) flows in the circuit of the solar cell if all the photons are absorbed by the cell and each photon produces one electron?

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Open Question

How are wavelength, frequency, and energy related for photons of light?

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Open Question

What is the longest wavelength of radiation with enough energy to break carbon-carbon bonds?

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Open Question

Hospital X-ray generators emit X-rays with wavelength of about 15.0 nanometers (nm), where 1nm = 10⁻⁹ m. What is the energy of a photon of the X-rays?

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Open Question

Calculate the energy of the violet light emitted by a hydrogen atom with a wavelength of 410.1 nm.

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Open Question

A bright violet line occurs at 435.8 nm in the emission spectrum of mercury vapor. what amount of energy, in joules, must be released by an electron in a mercury atom to produce a photon of this light?

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Open Question

How much energy (in kJ) do 3.0 moles of photons, all with a wavelength of 655 nm, contain?

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Open Question

Calculate the energy of the orange light emitted, per photon, by a neon sign with a frequency of 4.89 × 10¹⁴ Hz.

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Open Question

Calculate the energy of the green light emitted, per photon, by a mercury lamp with a frequency of 5.49 × 10¹⁴ Hz.