Spectroscopy and the Electromagnetic Spectrum

An atom emits a photon when an electron drops from a higher energy level to a lower energy level. Emission of which type of electromagnetic radiation indicates the smallest energy-level spacing among the choices?

• Radio wave
• Ultraviolet
• Visible
• Gamma ray
• X-ray

A student is told that electromagnetic radiation can be ordered by increasing photon energy as: radio < microwaves < infrared < visible < ultraviolet < X-rays < gamma rays. Which ordering lists the following three regions from lowest to highest photon energy: infrared, X-rays, and visible?

• Infrared < X-rays < visible
• X-rays < visible < infrared
• Visible < X-rays < infrared
• Infrared < visible < X-rays
• Visible < infrared < X-rays

A student compares two electromagnetic waves. Wave X is in the microwave region, and Wave Y is in the infrared region. Which comparison is correct for photon energy?

• Wave X and Wave Y photons must have the same energy if their amplitudes are equal
• Wave Y photons have higher energy than Wave X photons
• Photon energy cannot be compared without knowing the speed of the waves in vacuum
• Wave X and Wave Y photons must have the same energy if their intensities are equal
• Wave X photons have higher energy than Wave Y photons

A molecule absorbs radiation to undergo a transition. Transition X is induced by infrared radiation, and Transition Y is induced by ultraviolet radiation. Which statement best compares the energy changes for the two transitions?

• Transition Y involves a larger energy increase because UV photons are higher energy than IR photons
• Transition X involves a larger energy increase because IR has longer wavelength
• Energy increase depends only on intensity, so the brighter source causes the larger increase
• Both transitions involve the same energy increase because both are absorption processes
• Transition X involves a larger energy increase because IR radiation is felt as heat

A sample is analyzed using three different regions of the electromagnetic spectrum: microwave radiation (rotational transitions), infrared radiation (vibrational transitions), and ultraviolet radiation (electronic transitions). Which ordering lists these from lowest to highest photon energy?

• Microwave < infrared < ultraviolet
• Microwave < ultraviolet < infrared
• Infrared < microwave < ultraviolet

A student states: “If two beams of electromagnetic radiation have the same intensity, then they must have the same photon energy.” Which choice best evaluates the statement?

• The statement is incorrect because intensity changes the speed of the radiation.
• The statement is correct because all electromagnetic radiation has the same energy per photon.
• The statement is incorrect because photon energy depends on the region (frequency), not intensity.
• The statement is correct because intensity determines photon energy.
• The statement is correct because higher intensity always means higher energy per photon.

Two photons, Photon A and Photon B, are emitted from the same excited atom during different transitions. Photon A is in the visible region, and Photon B is in the ultraviolet region. Which statement is correct?

• Photon A has higher energy if its intensity is higher than Photon B’s intensity.
• Photon B has lower energy because ultraviolet light has a longer wavelength than visible light.
• They must have the same energy because both are emitted from the same atom.
• Photon A has higher energy because visible light is higher energy than ultraviolet light.
• Photon B has higher energy because ultraviolet light is higher energy than visible light.

In an experiment, a molecule absorbs electromagnetic radiation and undergoes a transition to a higher energy state. Absorption of infrared radiation causes one transition, while absorption of visible radiation causes another transition. Which absorbed radiation corresponds to the larger energy increase of the molecule?

• Infrared, because it is commonly used for molecular spectroscopy.
• Infrared, because infrared has higher photon energy than visible light.
• Visible, because visible light has higher photon energy than infrared radiation.
• Visible, but only if the visible light is more intense.
• Both, because any absorbed photon produces the same energy increase.

A sample emits two types of electromagnetic radiation: one in the microwave region and one in the X-ray region. Which comparison is correct?

• X-rays have lower photon energy than microwaves because X-rays are less intense in typical sources
• Microwaves have higher photon energy than X-rays because microwaves have shorter wavelength
• X-rays have higher photon energy than microwaves because X-rays have higher frequency
• Microwaves and X-rays have the same photon energy because both are electromagnetic waves
• Microwaves have higher photon energy than X-rays because microwaves can heat water