Spectroscopy: 3 experiments to see the rainbow by dividing the light
Things that are transmitted by waves, such as light and radio waves, have the property of wrapping around instead of going straight under certain conditions. Using this to separate light (creating a rainbow) is called spectroscopy. This time is a simple spectroscopic experiment.
Experiment 1: Light is applied to a CD to disperse it.
Light has the property of diffracting (wrapping around and bending) when it passes through a narrow gap or when it is reflected on a surface with a narrow groove. There are many narrow grooves on the CD. There are 625 lines per mm, and the distance between the two lines is 0.0016 mm. When light hits this narrow groove, it causes diffraction. The place where it is strengthened or weakened changes depending on the wavelength of light. In other words, the place where it is strengthened changes depending on the color, and the light is dispersed like a rainbow. It's a spectroscope that's too simple. This only reflects the sunlight onto the white paper.
Fig. 1 Fig. 2
It's easy to see the rainbow, but the principle is a bit difficult. It is the content to study in high school physics. When light is incident on something that is drawn at very fine intervals, such as a groove (actually a protrusion) on a CD, the object that is reflected in a certain angle is strengthened. It is known that the angle θ that is strengthened at this time is d sin θ = n λ.
Since the wavelength λ differs depending on the light, the red, green, and blue lights are strengthened at different angles. Figure 2
Experiment 2: Manufacture of a CD spectroscope
Therefore, if you set the angle to about 60 ° from the above formula, you can see from red to blue. Assemble a box like the one in the picture (the blueprint is in the PDF below) and look at it in a black tube so that you can easily see the rainbow. As shown in the lower right photo, the light is divided and looks like a rainbow.
I saw a rainbow with a spectroscope. In addition, I will talk about how to use this spectroscope. By examining the light in detail, you can investigate the substance of the light source. For example, when examining sunlight, there is no light of a specific wavelength. That is the black line in the figure below. It is called the Brown Forfer line. The atmosphere of the sun is caused by the absorption of certain light by certain light. You can investigate the material composition of the stars in the night sky.
From Wikipedia
experiment 3: Observation of absorption spectrum of plant leaves
The experiment itself is extremely simple, grind the leaves of the plant and extract the leaf pigment with ethanol. If you look at the sunlight through the extract, you can see what wavelength the leaves of the plant absorb and photosynthesize.
looking at the sunlight through the extract