CEM 141-Exam 1 UPDATED Study
ACTUAL QUESTIONS AND CORRECT
ANSWERS
Describe the relationship between the frequency, wavelength, and velocity (speed) of a wave. -
CORRECT ANSWER velocity (speed of light) = wavelength (m) x frequency (Hz or s^-1)
Draw and compare two waves of different frequency, wavelength, or amplitude. - CORRECT
ANSWER frequency: higher frequency if amplitudes are closer together, lower frequency if
they're further apart
wavelength: greater wavelength if amplitudes are further apart, shorter wavelength if waves are closer
together
amplitude: if the height of the wave increases, the amplitude is larger
Calculate any one (frequency, wavelength, or velocity) given the other two. Use appropriate units. -
CORRECT ANSWER know c=lambda (wavelength) x weird v (frequency)
Rank electromagnetic radiation (visible, gamma ray, UV, radio wave, IR, microwave, X-ray) in terms
of energy, wavelength, or frequency. - CORRECT ANSWER gamma rays, x rays, UV, visible
light (VIBGYOR), infrared, microwave, radio wave
left side: short wavelength, high frequency and energy
right side: long wavelength, low frequency and energy
Describe and identify experimental evidence for why electromagnetic radiation is a wave. -
CORRECT ANSWER Double slit experiment: waves interfere with each other to give that
striped pattern due to constructive and destructive interference (which happens in waves)
Make an argument (include claim, evidence, and reasoning) about why we can consider
electromagnetic radiation as a wave. - CORRECT ANSWER Electromagnetic radiation is a
wave and we can see this through the double slit experiment. Waves of light were shown upon a
barrier, and as they passed through each slit, they diffracted, which caused both constructive and
destructive interference. Due to this, the constructed/destructed waves made a striped pattern on the
back surface of the experiment. Since waves have constructive and destructive interference, we can
conclude that electromagnetic radiation (light) is a wave.
, Describe and identify experimental evidence for why electromagnetic radiation is a particle. -
CORRECT ANSWER Many metals emit electrons when electromagnetic radiation shines on
the surface. The light is transferring energy to the electrons at the metal's surface where it is
transformed into kinetic energy that gives the electrons enough energy to leave the atoms in the metal.
Only lights with higher frequencies allow for an electron to be ejected. If you increase the intensity of
that light, more electrons will fly off, however, if lower frequency light that does not cause the metal
to emit an electron are shone on the metal, no matter how intense, the metal will never emit an
electron. If electromagnetic radiation was only a wave, increasing the intensity of any light would
cause an electron to be emitted from the metal. This is how we know electromagnetic radiation is a
particle.
Using the photoelectric effect experiment, draw and explain graphs that show the number of electrons
ejected vs. frequency or wavelength of radiation that shines on the metal. - CORRECT ANSWER
purple/blue lights will eject electrons while red light will not
Calculate the energy of photons of a given frequency or wavelength (and vice versa). - CORRECT
ANSWER E= h (constant) x v (frequency)
Explain why the existence of photons (quantized light energy) explains the photoelectric effect. -
CORRECT ANSWER because the threshold frequency is the minimum energy required to emit
an electron; if photons do not have enough energy to emit an electron, an electron will not be emitted
regardless of intensity
Make an argument (include claim, evidence, and reasoning) about why we can consider
electromagnetic radiation as a particle. - CORRECT ANSWER Many metals emit electrons
when electromagnetic radiation shines on the surface. The light is transferring energy to the electrons
at the metal's surface where it is transformed into kinetic energy that gives the electrons enough
energy to leave the atoms in the metal. Only lights with higher frequencies allow for an electron to be
ejected. If you increase the intensity of that light, more electrons will fly off, however, if lower
frequency light that does not cause the metal to emit an electron are shone on the metal, no matter
how intense, the metal will never emit an electron. If electromagnetic radiation was only a wave,
increasing the intensity of any light would cause an electron to be emitted from the metal. This is how
we know electromagnetic radiation is a particle.
Explain how (and why) different atoms emit different wavelengths of light. - CORRECT ANSWER
each element has electrons of different energies; the energy changes between the energy levels
are also different, so each element will have a different emission and absorption spectra
ACTUAL QUESTIONS AND CORRECT
ANSWERS
Describe the relationship between the frequency, wavelength, and velocity (speed) of a wave. -
CORRECT ANSWER velocity (speed of light) = wavelength (m) x frequency (Hz or s^-1)
Draw and compare two waves of different frequency, wavelength, or amplitude. - CORRECT
ANSWER frequency: higher frequency if amplitudes are closer together, lower frequency if
they're further apart
wavelength: greater wavelength if amplitudes are further apart, shorter wavelength if waves are closer
together
amplitude: if the height of the wave increases, the amplitude is larger
Calculate any one (frequency, wavelength, or velocity) given the other two. Use appropriate units. -
CORRECT ANSWER know c=lambda (wavelength) x weird v (frequency)
Rank electromagnetic radiation (visible, gamma ray, UV, radio wave, IR, microwave, X-ray) in terms
of energy, wavelength, or frequency. - CORRECT ANSWER gamma rays, x rays, UV, visible
light (VIBGYOR), infrared, microwave, radio wave
left side: short wavelength, high frequency and energy
right side: long wavelength, low frequency and energy
Describe and identify experimental evidence for why electromagnetic radiation is a wave. -
CORRECT ANSWER Double slit experiment: waves interfere with each other to give that
striped pattern due to constructive and destructive interference (which happens in waves)
Make an argument (include claim, evidence, and reasoning) about why we can consider
electromagnetic radiation as a wave. - CORRECT ANSWER Electromagnetic radiation is a
wave and we can see this through the double slit experiment. Waves of light were shown upon a
barrier, and as they passed through each slit, they diffracted, which caused both constructive and
destructive interference. Due to this, the constructed/destructed waves made a striped pattern on the
back surface of the experiment. Since waves have constructive and destructive interference, we can
conclude that electromagnetic radiation (light) is a wave.
, Describe and identify experimental evidence for why electromagnetic radiation is a particle. -
CORRECT ANSWER Many metals emit electrons when electromagnetic radiation shines on
the surface. The light is transferring energy to the electrons at the metal's surface where it is
transformed into kinetic energy that gives the electrons enough energy to leave the atoms in the metal.
Only lights with higher frequencies allow for an electron to be ejected. If you increase the intensity of
that light, more electrons will fly off, however, if lower frequency light that does not cause the metal
to emit an electron are shone on the metal, no matter how intense, the metal will never emit an
electron. If electromagnetic radiation was only a wave, increasing the intensity of any light would
cause an electron to be emitted from the metal. This is how we know electromagnetic radiation is a
particle.
Using the photoelectric effect experiment, draw and explain graphs that show the number of electrons
ejected vs. frequency or wavelength of radiation that shines on the metal. - CORRECT ANSWER
purple/blue lights will eject electrons while red light will not
Calculate the energy of photons of a given frequency or wavelength (and vice versa). - CORRECT
ANSWER E= h (constant) x v (frequency)
Explain why the existence of photons (quantized light energy) explains the photoelectric effect. -
CORRECT ANSWER because the threshold frequency is the minimum energy required to emit
an electron; if photons do not have enough energy to emit an electron, an electron will not be emitted
regardless of intensity
Make an argument (include claim, evidence, and reasoning) about why we can consider
electromagnetic radiation as a particle. - CORRECT ANSWER Many metals emit electrons
when electromagnetic radiation shines on the surface. The light is transferring energy to the electrons
at the metal's surface where it is transformed into kinetic energy that gives the electrons enough
energy to leave the atoms in the metal. Only lights with higher frequencies allow for an electron to be
ejected. If you increase the intensity of that light, more electrons will fly off, however, if lower
frequency light that does not cause the metal to emit an electron are shone on the metal, no matter
how intense, the metal will never emit an electron. If electromagnetic radiation was only a wave,
increasing the intensity of any light would cause an electron to be emitted from the metal. This is how
we know electromagnetic radiation is a particle.
Explain how (and why) different atoms emit different wavelengths of light. - CORRECT ANSWER
each element has electrons of different energies; the energy changes between the energy levels
are also different, so each element will have a different emission and absorption spectra
