Phonetics and the IPA, Chapter 1, Exercise 1
Sample answer for Received Pronunciation (RP); yours may differ with your accent.

bead   [biːd]  - vowel [iː]
bread  [bɹɛd]  - vowel [ɛ]
break  [bɹeɪk] - diphthong [eɪ]
heart  [hɑːt]  - vowel [ɑː]
earth  [ɜːθ]   - vowel [ɜː]

Five different vowel sounds from the letters "ea". Other words with each sound:
[iː]: sea, meat      [ɛ]: head, dead      [eɪ]: steak, great
[ɑː]: hearth (RP), hearty      [ɜː]: learn, pearl

Lesson: the same letters stand for several sounds, so spelling cannot record sound.
(Transcriptions are from my knowledge of RP and have not been checked against a dictionary.)