X-ray films designed to be most sensitive to which in the blue-violet spectrum for use with calcium tungstate intensifying screens?

• A. Light
• B. Ultraviolet
• C. Radio waves
• D. Heat

Answer: (A)

When an X-ray image is formed with calcium tungstate screens, the screen converts X-rays into visible blue-violet light. The film used with these screens is formulated to be most sensitive to that light, meaning its silver halide crystals are highly responsive to blue-violet photons. This blue-sensitive exposure is what releases electrons to create the latent image in the emulsion, which later becomes a visible image after processing. Because the emission from calcium tungstate is in the blue-violet range, the film’s peak sensitivity is in that part of the spectrum, i.e., to light. Ultraviolet, radio waves, and heat do not produce the chemical changes in the film needed to form the latent image in this setup.