GMAT CR: “Strengthen” Question of the Day!

A broken shard of glass found in the laboratory of the famed physicist Alhazen has a polished surface that separates out the green and blue spectrums of white light, a key characteristic of a dispersive prism, which separates white light into all its constituent spectral components. Scientific historians, based on this finding, are revising their histories in order to give Alhazen, the “father of modern optics,” credit for the discovery of the dispersive prism, which was thought to have been discovered many years later.

Which of the following, if true, most strongly supports the historians’ decision to revise the history of optics?

A. Dispersive prisms were the only type of prism that was theorized about in the scientific era in which Alhazen lived.

B. The piece of glass from which the shard broke, if unbroken, would have been just large enough to separate out the entire spectrum of white light into its spectral components.

C. The piece of glass was a combination of flint glass, which was known to have been used by Alhazen to craft lenses in his laboratory, and crown glass, another popular type of glass throughout history.

D. Dispersive prisms are the simplest and most common objects that are able to divide white light into its constituent spectral components.

E. Several glass objects that are known to have some properties of a dispersive prism have been found to be older than the glass piece in Alhazen’s laboratory.


Conclusion: Historians give A credit for prism.

Evidence: Glass found that has characteristic of prism.

Assumption: Glass not there by accident; glass definitely means A “discovered” prism.

Question: What STRENGTHENS?

Prediction: Anything that links this glass to the prism, removes coincidence.

A – Other prisms out of scope.
B – This connects the glass to the prism.
C – The type of glass is irrelevant.
D – This is just a fact about the prism.
E – This would weaken, since it makes the glass/prism link less strong.

The answer is (B).