A lower coupon bond pays you less cash along the way, meaning more of its total value is tied up in that single **par value payment at maturity**. That distant lump sum is more sensitive to interest rate changes than frequent coupon payments.

A higher coupon bond pays you more cash sooner — those early payments are less affected by rate changes, so the overall price is more stable.

The two rules together:

- **Same coupon, different terms** → longer term is more volatile
- **Same term, different coupons** → lower coupon is more volatile

Think of it this way: **the less cash you get upfront, the more exposed you are to rate changes.**