Photoelectric effect.

Qualitative demonstrations of photoelectric effect, using sun and carbon as sources. Experiments measure energy of photoelectron emitted from a potassium surface. With John Strong, assisted by William T. Plummer. The film was directed by Gene Kearney, noted for his film adaptation on Conrad Aiken's 'Silent Snow, Secret Snow' ( https://archive.org/details/silent_snow_secret_snow )