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Description: With the Autoradiograph activity, students gain a better understanding of the different types of radiation, alpha, beta, and gamma. This is a way that students can detect invisible emissions.
This experiment is best used by students working in groups.
1-5 (sun paper)
Disciplinary Core Ideas (DCI, NGSS)
5-PS1-1, MS-PS1-1, MS-PS1-4, HS-PS1-8, HS-PS4-2, HSPS4-5
Time for Teacher Preparation
30-60 minutes – To gather materials and set-up
1 Week to develop the autoradiograph
30-60 minutes (1 Class Period) for set-up
30-60 minutes (1 Class Period) to develop the autoradiograph
Science and Engineering Practices (NGSS)
Cross Cutting Concepts (NGSS)
Often used to detect radiation by imaging its emissions, an autoradiograph is a representation of where radioactive substances are located. The image can be projected onto a medium such as an x-ray film, nuclear emulsion, or even photographic film. Autoradiography, which can also be digital, is used in many cases for biological and medical applications. In contrast to other methods of detecting radiation, they can show the locations of radioactive materials in a sample. The images can therefore be used with biological specimens labeled with such materials, to track cellular activity for example.
In its basic form, an autoradiograph can require film to be exposed overnight. Radioactivity is detected through bands on an image, which are produced as particles hit crystals of silver halide. The images on the film typically depend on the activation of the crystals and the effects of particles on a gel. If each crystal is insulated by a gelatin capsule, then a permanently developed image can accurately show the sample and where it is radioactive.
An autoradiograph is often taken after biological tissue is exposed to a radioactive substance, left for a certain period of time, and examined under a microscope. Sections can be cut and a photographic image can be developed as a radioisotope decays. Samples are often stained to enhance the detail and to see the grains of silver that react with the substance. The resulting autoradiograph can be recorded and kept on file as part of an experiment or test.
While a solid film was typically used in the past, a liquid emulsion is often used in the 21st century to make an autoradiograph. This technique can take less time to complete. Liquid can flow and make the thickness of the sample uneven, but following the basic steps for coating slides and developing the film can dry the sample appropriately. A phosphor-imager screen can help detect radioactivity in gel quicker than x-ray film. It is typically used with electronic instruments and a computer system that can digitally image the sample.
Autoradiographs can show radioactive particles attached to enzymes or integrated into nucleic acid. Metabolic processes can be tracked in cells when images of radioactive particles are compared. Researchers can track proteins, photosynthesis, and the division and movement of cells. Sequences of deoxyribonucleic acid (DNA) can be tracked. Autoradiography DNA is often used to monitor cell cycles and track the progress of viruses to analyze their behavior.
NOTE: You can use the three radiation sources on one film sheet in lieu of the key and Coleman lantern mantle, Fiesta®ware plate, or a radium-dial clock. Students will find that only the beta and gamma sources will expose the film. This is because the paper surrounding the film shields alpha radiation.
NOTE: Elementary school students could try to perform this experiment using SunSensitive paper rather than Polaroid film. The SunSensitive paper reacts to UV sunlight and would be a good substitution for Polaroid film for this experiment.
NGSS Guided Inquiry
Student Data Collection Sheets
Students should label sources and type of radiation on film
Post Discussion/Effective Teaching Strategies
Questions provided on the Student Data Collection Sheets
Have students identify an unknown source by experimenting with shielding, different sources, and different types of film.
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