Here's why:

* pH Scale: The pH scale measures acidity, with lower numbers indicating higher acidity.

* Orange Juice pH: Orange juice typically has a pH of around 3.5 to 4.0.

* Pepsi pH: Pepsi has a pH around 2.5.

While Pepsi has a lower pH, meaning it's more acidic than orange juice, it's important to note:

* Acidity vs. Concentration: Pepsi's acidity comes mainly from phosphoric acid, which gives it a sharp, tangy flavor. However, the *concentration* of acid in Pepsi is less than in orange juice.

* Citric Acid: Orange juice contains citric acid, which is also responsible for its tartness. Citric acid is naturally present in citrus fruits and contributes to their acidic nature.

So, while Pepsi is *more acidic* on the pH scale, the *concentration* of acid in orange juice is likely higher, making it potentially more damaging to teeth or other surfaces.