Chapter 16: Problem 21

a. What is the energy in joules associated with photons that have a wavelength matching that of the color blue in the visible spectrum? b. Repeat part (a) for the color red. c. Do the results confirm the fact that the shorter the wavelength the higher the energy level? d. Is light in the ultraviolet range more dangerous in regard to skin cancer than those in the infrared range? Why? e. Can you guess why fluorescent lights are used for growing plants in a dark environment?

Short Answer

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a) The energy associated with blue photons is higher due to its shorter wavelength compared to red. b) The energy associated with red photons is lower due to its longer wavelength. c) Yes, the results confirm that the shorter the wavelength, the higher the energy level. d) Yes, UV light is more dangerous than IR in regard to skin cancer because it carries more energy. e) Fluorescent lights are used for growing plants in a dark environment because they provide light within the photosynthetic spectrum, are energy-efficient and emit less heat.

Step by step solution

Calculate Energy for Blue Light

The energy of a photon can be calculated using the formula \(E = hv\), where \(h\) is the Planck's constant and \(v\) is the frequency. Frequency can also be obtained from the speed of light \(c\), wavelength \(\lambda\) with the formula \(v = c/\lambda\). For blue light, the wavelength is about 450 nm. Substituting the values into the formulas, the energy can be computed.

Calculate Energy for Red Light

Using the same formulas as in Step 1, we can calculate the energy for red light. The approximate wavelength for red light in the visible spectrum is 700 nm.

Compare the Energy Levels

By comparing the calculated energy levels for blue and red light, it can be confirmed whether the energy level is higher for shorter wavelength light.

Discuss the Danger of Ultraviolet and Infrared Light

The dangers of ultraviolet (UV) and infrared (IR) light can be analyzed by examining their energy levels. UV light falls on the higher frequency (shorter wavelength) side of the light spectrum, while IR is on the lower frequency (longer wavelength) side. As energy is proportional to frequency, this implies that UV light carries more energy, potentially causing more damage to skin cells hence increasing skin cancer risk.

Discuss the Use of Fluorescent Lights

Fluorescent lights are often used for growing plants in a dark environment because they can provide light within the spectrum that plants need to photosynthesize. Furthermore, they are more energy-efficient and always emit less heat, which is beneficial for maintaining ideal plant growth temperatures.

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Short Answer

Step by step solution

Calculate Energy for Blue Light

Calculate Energy for Red Light

Compare the Energy Levels

Discuss the Danger of Ultraviolet and Infrared Light

Discuss the Use of Fluorescent Lights

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