1. Explain the mathematical relationship among the speed, wavelength, and
the frequency of the electromagnetic radiation.
2. Discuss the dual wave-particle nature of light.
Duration: 45 minutes followed by 10 minute quiz the following class.
Intended audience are 9th grade standard chemistry class.
Properties of light
In the twentieth century studies revealed a relationship between light and an atom’s electron. This led to the understanding of the nature of energy, matter, and atomic structure. Before 1900, scientists thought light behaved solely as a wave. Later it was discovered that light also has particle like characteristics.
The wave description of light
Visible light is a kind of electromagnetic radiation. Other kinds of electromagnetic radiation include X-ray, ultraviolet, infrared, microwaves, and radio waves. Together all the forms of electromagnetic radiation forms the electromagnetic spectrum fight.
All forms of electromagnetic radiation move at a constant speed of 3.00x108 through vacuums and at slightly slower speed through matter.
All electromagnetic radiation have wave motion which repetition in nature and characterized by a measurable properties of
1. Wavelength (λ)
2. Frequency (v)
Wavelength: is the distance between corresponding points on adjacent waves and has a distance unit.
Frequency is defined as the number of waves that passes a given point in one second, and has a unit called hertz (H2). Frequency is expressed in wave/sec.
Frequency and wavelength are mathematically related to each other as follows.
c=λ v
Because c is the same for all electromagnetic radiation, the product λ v is constant. Consequently λ is inversely related to v. In other words, as the wavelength of light increases, its frequency decreases.
Questions:
In what form does the electromagnetic radiation travel?
From fig. 1 what portion of the electromagnetic spectrum is visible to the human eye?
Arrange the visible light color from longest to shortest wavelengths?
Calculate the speed of light from the data for infrared radiation, using the following equation: c=λ v. How does this compare to the known value (3.00x 108 m/s).